Leading ozone scientist says more climate surprises likely

Issued on: 21/03/2023 -

Solomon led an ozone expedition to Antarctica in the mid-1980s 

© Handout / Susan SOLOMON/AFP/File


Paris (AFP) – Susan Solomon, a leading scientist in the fight to tackle the Antarctic ozone hole, says people are now getting worried enough to spur climate action.

The former expert for the UN's Intergovernmental Panel on Climate Change said the organisation's final instalment of a major series of reports, released Monday, would not be the "last word" on warming.

IPCC warned that climate change impacts are hitting faster than expected and the key 1.5 degree-Celsius warming limit could be reached in the early 2030s.

Solomon, a professor at MIT, said in an interview that more surprises were likely in store.

Her own research had delivered a recent "shocker" that Australia's massive 2019-20 wildfires combined with lingering remnants of the chlorofluorocarbons (CFCs) still in the atmosphere to erode the ozone layer -- Earth's protective shield from damaging ultraviolet radiation.

The following interview has been edited for length and flow:

Q: Did it feel like a crisis when the ozone hole was discovered?

A: It was a huge moment. The only thing you could compare it to would be if a piece of Greenland suddenly fell off into the sea and people were waiting for the three metres of sea level rise to show up on their doorstep.

All of a sudden you had 50 percent less ozone over Antarctica at certain times of year. And we did not know why.

I was 29 years old when the British Antarctic Survey discovered the ozone hole in 1985.

In 1986, I led the national ozone expedition to Antarctica. We made measurements of everything that we could think of: ozone itself, but also chlorine monoxide, chlorine dioxide, all of the ozone eating molecules and we were able to show that they were completely out of whack.

My idea was that maybe the reason this was happening was because of polar stratospheric clouds and surface chemistry. That turned out to be right.

Q: The Montreal Protocol (phasing out CFCs and other ozone depleting molecules) was signed in 1987. What enabled governments to act so quickly?

UN climate experts say the impacts of warming are coming faster than expected

© TORSTEN BLACKWOOD / AFP/File

A: Three P's -- It was personal to people, because skin cancer and cataracts are scary. And it was perceptible because you could see these dramatic images on TV. It could easily be explained. And practical solutions were found pretty quickly.

Had we not stopped making these molecules, you would have massive ozone depletion worldwide. Overall, it has been a remarkable science, policy, and public success story.

Q: Why has climate change not had the same urgency?

A: People are beginning to get concerned enough about climate change, particularly the young. That is a tremendous spur to politicians.

The biggest problem is that people believe the solutions are not practical, but it's not at all true. People have to recognise how much more it's going to cost us if we don't do anything.

It's also too easy to tie climate change up with the culture wars, or whatever your social issue of the moment is.

We didn't have that with the ozone.

I was once in an IPCC meeting about chlorofluorocarbons with a delegate from a Middle Eastern country that produces a lot of oil. I asked him if his government had any concerns and he said: "No, we don't really care what's in the air conditioner, as long as it makes it cold".

The chemical companies could make other compounds. The problem with the fossil fuel companies is they're not going to be the ones to make solar panels.

Q: What are the key unanswered questions on climate change?

A: There's a lot of work going on now on understanding how storm tracks are going to change. Are we going to have more extreme Arctic air cold snaps? It might not be the issue you expected, but it's an issue.

Melting of the polar ice sheets -- how fast is that going to happen? There's a lot of uncertainty. It affects people on coastlines and island states all around the world.

The impact on the food and water supply -- there are open questions on both.

Things that involve the crossover between biology and physics are often the most difficult to understand. There's a 30 percent decline in the insect population worldwide going on right now. We really don't know why.

It's a great time to be a climate scientist, but on the other hand, it seems to me that every year something important and scary is happening.

© 2023 AFP

TikTok says half of Americans use site as ban threat looms

TikTok says it has 150 million monthly users in the United States -- a sharp increase

Washington (AFP) – TikTok CEO Shou Zi Chew said Tuesday that US user numbers had soared to 150 million -- almost half the total population -- as he prepared to fight at US Congress for the Chinese owned site's future.

Chew will give testimony before the House Energy and Commerce Committee Thursday where he is set to face a barrage of questions over allegations by both Republicans and Democrats that the app is beholden to the Communist Party in Beijing.

The company has also confirmed reports that the White House gave TikTok an ultimatum to part ways with its Chinese owners or face a US ban.

"Today, I'm super excited to announce that more than 150 million Americans are on TikTok. That's almost half of the US coming to TikTok to connect, to create, to share, to learn or just to have some fun," Chew said in a TikTok post.

This was up from TikTok's previous measure in 2020 that 100 million users came to the video sharing site every month, which already made it one of the most popular.

Chew also asked the app's devoted users to "let me know in the comments what you want your elected representatives to know about what you love about TikTok."

"Some politicians have started talking about banning TikTok. Now this could take TikTok away from all 100 and 50 million of you," Chew said.

The Singaporean CEO said he would share with Congress "all that we're doing to protect Americans using the app," in a reference to a proposal called Project Texas that would guarantee a special handling for the data of US users.

TikTok has consistently denied sharing data with Chinese officials and says it has been working with US authorities for more than two years to address national security concerns.

Time spent by US users on TikTok has surpassed that spent on YouTube, Facebook, Instagram or Twitter and it is closing in on streaming titan Netflix, according to market tracker Insider Intelligence.

21/03/2023 

© 2023 AFP

AMERICAN EVANGELICAL INFLUENCE

Uganda to vote on tough anti-gay bill
AFP
Tue, Mar 21, 2023


Uganda's parliament was due to vote Tuesday on anti-gay legislation which proposes tough new penalties for same-sex relations in a country where homosexuality is already illegal.

Under the proposed law, anyone in the conservative East African nation who engages in same-sex activity or who identifies publicly as LGBTQ could face up to 10 years in prison.

"The Anti-Homosexuality Bill is ready and will be tabled (put) before parliament for a vote this afternoon," said Robina Rwakoojo, chair of the legal and parliamentary affairs committee, which has been studying the legislation.

The legislation enjoys broad public support in Uganda and reaction from civil society has been muted following years of erosion of civic space under President Yoweri Museveni's increasingly authoritarian rule.

Nevertheless, Museveni has consistently signalled he does not view the issue as a priority and would prefer to maintain good relations with Western donors and investors.

Discussions about the bill in parliament have frequently been laced with homophobic rhetoric, with Museveni last week referring to gay people as "these deviants."

"Homosexuals are deviations from normal. Why? Is it by nature or nurture? We need to answer these questions," the 78-year-old told lawmakers.

"We need a medical opinion on that. We shall discuss it thoroughly," he added, in a manoeuvre interpreted by analysts and foreign diplomats as a delaying tactic.

"Museveni has historically taken into account the damage of the bill to Uganda's geopolitics, particularly in terms of relations with the West, and in terms of donor funding," said Kristof Titeca, an expert on East African affairs at the University of Antwerp.

"His suggestion to ask for a medical opinion can be understood in this context: a way to put off what is a deeply contentious political issue," Titeca told AFP.

On Saturday, Uganda's attorney general Kiryowa Kiwanuka told the parliamentary committee scrutinising the bill that existing colonial-era laws "adequately provided for an offence".

- 'Unconstitutional provisions' -

As parliamentary proceedings got under way, legislator Fox Odoi-Oywelowo, who belongs to Museveni's National Resistance Movement party, urged lawmakers not to pass the legislation.

The bill "contains provisions that are unconstitutional, reverses the gains registered in the fight against gender-based violence and criminalises individuals instead of conduct that contravenes legal provisions", he said, as some MPs repeatedly tried to shout over him.

"It was introduced during a time when anti-homosexual sentiments have been whipped up across the country and is not based on any evidence to show that incidents of homosexuality have increased and require additional legislative intervention," he added.

In recent months, conspiracy theories accusing shadowy international forces of promoting homosexuality have gained traction on social media in Uganda.

Frank Mugisha, executive director of Sexual Minorities Uganda, a leading gay rights organisation whose operations were suspended by the authorities last year, told AFP earlier this month he had already been inundated with calls from LGBTQ people over the new bill.

"Community members are living in fear," he said.

Last week, police said they had arrested six men for "practising homosexuality" in the southern lakeside town of Jinja.

Another six men were arrested on the same charge on Sunday, according to police.

Uganda is notorious for intolerance of homosexuality -- which is criminalised under colonial-era laws.

But since independence from Britain in 1962 there has never been a conviction for consensual same-sex activity.

In 2014, Ugandan lawmakers passed a bill that called for life in prison for people caught having gay sex.

The legislation sparked international condemnation, with some Western nations freezing or redirecting millions of dollars of government aid in response, before a court later struck down the law on a technicality.

gm-str/amu/txw/bp

Uganda's parliament set to vote on tougher anti-LGBTQ bill

Lawmakers are voting on the bill as President Yoweri Museveni calls for investigations into homosexuality in the country. Uganda already has some of the most draconian anti-LGBTQ legislation in the world.

Members of parliament in Uganda on Tuesday were set to vote on a bill that will criminalize identifying as LGBTQ, with some lawmakers in the conservative East African nation saying that the nationwide ban on same-sex relationships does not go far enough.

What did the bill entail?

The bill, introduced earlier this month, proposes tough new penalties against sexual minorities.

Under the new proposed legislation, anyone who engages in "same-sex activity" or who identifies as LGBTQ could face up to 10 years' imprisonment.

"The homosexuals are deviations from normal. Why? Is it by nature or nurture? We need to answer these questions," President Yoweri Museveni said when MPs asked him to comment on the bill.

The proposed law aims to allow Uganda to fight what it perceives as "threats to the traditional, heterosexual family."

VIDEO Uganda set to toughen anti-gay legislation  03:12

Homophobia and anti-trans sentiment are deeply entrenched in the highly conservative and religious nation, with same-sex romantic relationships punishable by up to life imprisonment.

More than 30 African countries have similar statutes, but Uganda's law, if passed, would be the first to criminalize merely identifying as lesbian, gay, bisexual, transgender or queer (LGBTQ), according to Human Rights Watch.

It also criminalizes what it calls the "promotion" of homosexuality and "abetting" and "conspiring" to engage in same-sex relations.

Lawmakers in Uganda have voted on anti-gay bill

Image: Sally Hayden/ZUMA/imago images

Strong condemnation from rights groups

The bill has drawn sharp criticism from human rights organizations.

The law is similar to one passed in 2013 that stiffened some already-existing penalties and criminalized lesbian relationships. It drew intense international outrage for originally proposing to punish homosexuality with the death penalty. This was later revised to life in prison.

However, it was quickly struck down by a domestic court on procedural grounds.

According to Oryem Nyeko a researcher at Human Rights Watch in Uganda, "One of the most extreme features of this new bill is that it criminalizes people simply for being who they are, as well as further infringing on the rights to privacy, and freedoms of expression and association that are already compromised in Uganda."

DW

'We call him Emperor Putin': Beijingers share views as Xi visits Russia

Issued on: 21/03/2023 - 

'We call him Emperor Putin': Beijingers share views as Xi visits Russia (2023) © AFP / France 24

03:04

Video by: Juliette MONTILLY

People in the Chinese capital Beijing share their thoughts on Russia and the war in Ukraine, on the day that Russian President Vladimir Putin and Chinese President Xi Jinping are set to hold a second day of talks in Moscow.

Student killed, hundreds arrested in Kenya protests

Issued on: 21/03/2023

02:16

A university student in Kenya was killed and more than 200 people arrested in nationwide protests against President William Ruto's government over high living costs on Monday, police said.

A public probe of foreign election interference should also look at India, Sikh organizations say

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Spokesperson for Sikh group says Ottawa tends to avoid

confrontations with India

Catharine Tunney · CBC News · Posted: Mar 21, 2023 

Prime Minister Justin Trudeau and Indian Prime Minister Narendra Modi wave during a family photo at the G7 Summit in Schloss Elmau on Monday, June 27, 2022. (Paul Chiasson/Canadian Press)

As former governor general David Johnston considers whether to recommend a public inquiry into Chinese government election meddling, groups representing Sikh Canadians say India's interference in Canadian politics also demands scrutiny.

"We don't feel like we as a nation, as a country, have even acknowledged India as a problem in that form," said Moninder Singh, acting spokesperson for the British Columbia Gurdwaras Council, which advocates for the political concerns of Sikhs in Canada.

"People, I think, in our government feel compelled to bend to a certain degree, to not piss India off."

Opposition parties have been calling on the federal government to announce a public inquiry into foreign election interference in response to Globe and Mail reports that say the Chinese Communist Party attempted to ensure the Liberal Party won a minority government in the 2021 election.

Reporting by Global alleges intelligence officials warned Prime Minister Justin Trudeau that the Chinese government's interference campaign included funding a "clandestine network of at least 11 federal candidates running in the 2019 election" — an allegation Trudeau has denied.

• Trudeau calls David Johnston 'unimpeachable' as Conservatives attack his impartiality

• Conservatives attempt to force top Trudeau aide to testify on Beijing interference

Last week, the government appointed Johnston to the role of "special rapporteur" investigating the accusations and said he could recommend a public inquiry.

The British Columbia Gurdwaras Council teamed up with the Ontario Gurdwaras Committee to publish a report Monday calling out alleged Indian interference in Canada's politics.

"These activities include infiltrating Sikh Gurdwaras, recruiting informants and agent provocateurs within the community, deceptively interjecting the Indian narratives into Canadian media reporting, and influencing Canadian diplomats, security officers and MPs," it reads.

Moninder Singh is a spokesperson for the British Columbia Gurdwaras Council, which advocates for the political concerns of Sikhs in Canada. (Tina Lovgreen/CBC)

"The ultimate goal of such operations has been to discredit Sikh support for the Khalistan movement in Canada."

The report urged the government to look at other countries' efforts to interfere in Canadian politics.

Singh said he wants a public inquiry to examine how India's intelligence sector uses consulates and embassies, and how they operate within diaspora communities.

"I think if it gets into the public domain, classifying India as a player on that, I think the first piece is acknowledging the problem. And only then can the problem be dealt with," he said.

Monday's report summarized multiple public reports and media stories over the years suggesting Canadian intelligence agencies have been aware of India's attempts to interfere in Canadian affairs.

NSICOP's report into India highly redacted 

A 2018 report by the National Security and Intelligence Committee of Parliamentarians (NSICOP) looked at tensions between Canada and India and made six findings regarding foreign interference — all of which were redacted from the public report.

The committee, made up of MPs and senators from multiple parties with clearance to view classified information, reviewed Trudeau's infamous trip to India in 2018. The trip became mired in controversy when Jaspal Atwal — convicted of trying to assassinate an Indian cabinet minister in B.C. in 1986 — was invited to dine with Trudeau at a formal event hosted by the Canadian High Commissioner in Delhi.

Last week, the government appointed former governor general David Johnston to the role of "special rapporteur" to investigate claims of foreign election meddling and possibly recommend a public inquiry. (Sean Kilpatrick/Canadian Press)

Daniel Jean, the prime minister's national security and intelligence adviser at the time, told reporters on background that rogue political elements in India may have arranged Atwal's invitation to embarrass Trudeau and make him seem sympathetic to Sikh extremism.

"We came to the conclusion that there was a very high probability of an orchestrated disinformation campaign to tarnish Canada," he told a committee back in 2018.

Ahead of the 2019 election, CBC News reported that intelligence services were monitoring efforts by six countries — including India — to influence the election campaign. Sources said an integrated intelligence unit had been giving Canadian political parties bi-weekly briefings about foreign actors' activities in Canada.

The Canadian Press reported senior bureaucrats were warned that China and India likely would lean on their diaspora communities to advance their own agendas.

The British Columbia Gurdwaras Council and the Ontario Gurdwaras Committee are calling on the federal government to take a tougher approach on the foreign interference file — legally, through the Criminal Code and the Canada Elections Act, and diplomatically, by declaring diplomats persona non grata where the evidence warrants their ejection.

Their report also calls on national security agencies to disclose relevant information about India's record of election meddling and political interference in Canada.

WATCH | National security adviser explains the India briefing to reporters 

National Security Adviser Daniel Jean tells the Public Safety committee why he briefed the media about the Jaspal Atwal affair

"Declassified summaries of this information are imperative to educate the general public about the realities of foreign interference in Canada while ensuring the safety, security and confidence of vulnerable ethnocultural groups like the Sikh community," says the report.

"Indian foreign interference not only impacts Sikhs as a racialized group by persuading governments to repress vulnerable communities, but it also emboldens Indian officials to continue interfering in foreign states with impunity while violating human rights in Punjab."

The Canadian Security and Intelligence Service (CSIS) did not respond to CBC's request for comment.

"We don't necessarily know what's going on in the intelligence community and we can't know in many ways," said Singh. "But at the same time, the constant non-recognition of this issue paints a different picture for us."

The High Commission of India also did not respond to CBC's request for comment. 

Trudeau's rocky relationship with Modi

Singh has been vocal in his support for an independent Khalistan, a separate homeland for Sikhs. He said Canada's reluctance to call out current and previous Indian governments might be tied to trade issues, given that India has one of the fastest-growing economies in the world.

"You can acknowledge China, you can acknowledge Russia. What is the issue [with] acknowledging India?" he said. 

Trudeau's government has had a fraught relationship with the Indian government during his time in office. It has been accused of being soft on the Khalistan movement and of harbouring separatist ministers in his cabinet.

Back in 2019, an official in Prime Minister Narendra Modi's government accused the Liberal leader of kowtowing to Sikh voters after a reference to Sikh extremism was removed from a terrorism threat report.

Capt. Amarinder Singh, then the chief minister of Punjab, called the move "a threat to Indian and global security."

A few years earlier, Amarinder Singh snubbed cabinet minister Harjit Sajjan and accused him of being a "Khalistani sympathizer."

"Canada supports one, united India and that we are unanimous as a government, as ministers, on this issue," Trudeau said at the time.

According to a briefing cited in the NSICOP report, CSIS believes "the threat from Sikh extremists in Canada peaked in the mid-1980s and declined thereafter."

Thousands mourn Syria Kurd civilians killed by pro-Turkish fighters

AFP
Tue, March 21, 2023 a


Thousands of angry Kurds rallied in rebel-held northern Syria on Tuesday after pro-Turkish fighters killed four fellow Kurds who were celebrating their Nowruz new year festival, an AFP correspondent reported.

"They killed my children for no reason," Kuli Maho, 70, told AFP as she wept for her three sons and grandson.

Some people waved Kurdish flags as they gathered for the funeral procession in the border town of Jindayris and neighbouring villages in Aleppo province, an area that was badly affected by last month's devastating earthquake.

On Monday evening, fighters of the US-sanctioned Ahrar al-Sharqiya group opened fire on people who had lit a fire for Nowruz, killing four of them and wounding three, according to Britain-based monitoring group, the Syrian Observatory for Human Rights.

Residents told AFP that fighters of the Sharqiya Army, a splinter group of Ahrar al-Sharqiya, had carried out the killings.

Both factions are part of a coalition of Ankara-backed rebel groups known as the Syrian National Army.

"They beat us, they have no conscience," added Maho, who said she and her family had been living in a tent since the February 6 quake.

Jindayris was seized by Turkey and its Syrian rebel proxies in a 2018 offensive that drove Kurdish-led fighters -- and much of the resident Kurdish civilian population -- from the nearby Afrin area.

"They treat us like fourth or fifth class citizens," said protester Abu Jan, 42, referring to pro-Ankara factions that control the area.

"We can't move freely, they control everything and oppress us," he said.

"Nowruz is a national holiday, let us celebrate."

Some mourners huddled around bonfires set up for a Nowruz celebration overshadowed by the bloodshed.

Also known as Persian New Year, the Nowruz festival marks the start of spring and is celebrated by peoples of different ethnicities and faiths across the Middle East and beyond.

The US Treasury sanctioned Ahrar al-Sharqiya in July 2021.

Fighters from the group had pulled a 35-year-old Syrian Kurdish politician, Hevrin Khalaf, from her car and shot her dead in a possible war crime, according to the United Nations human rights office.

Elham Ahmad, a senior official of the Kurdish administration that retains control of much of the northeast, accused "Turkey and terrorist factions" it backs of "crimes against humanity" in the Afrin area.

Afrin is one of a number of formerly Kurdish-controlled areas of northern Syria that Turkey cleared of Kurdish-led fighters in successive cross-border operations.

str-rh/aya/lg/kir

PKK

YPJ/YPG

MINING IS NOT SUSTAINABLE

More upheaval at owner of NWT’s Nechalacho rare earths mine

Published: March 20, 2023 

OLLIE WILLIAMS

Nechalacho mine owner Vital Metals is parting company with managing director John Dorward, just months after appointing him.A view of the Nechalacho mine. Sarah Pruys/Cabin Radio

Dorward succeeded Geoff Atkins, who was abruptly dismissed in August. On Monday, Vital said Dorward had resigned as a director with immediate effect and would work three months’ notice as chief executive.

No explanation was given.

Vital’s chairman, Evan Cranston, left the board last month on the premise that Dorward’s arrival marked “the time for me to hand the reins over to the new team.”

Dorward, appointed in November, just completed a series of high-profile promotional engagements for Vital. He showed Prime Minister Justin Trudeau around the company’s Saskatoon rare earths processing facility, then hosted US ambassador to Canada David L Cohen at a critical minerals summit.

John Dorward, right, with US ambassador to Canada David L Cohen. David Connelly/Vital Metals

Richard Crookes, Vital’s interim chairman, said in a Monday news release that Dorward had “worked with the board and management team over the past few months to develop a new strategy for the business, which the management team will continue to implement.”

Who that management team now is was not immediately clear. Vital said it would commence an “international search” for a new chief executive.

Late last year, Vital said it was “pivoting strategy” at its NWT rare earths mine, east of Yellowknife, to place more emphasis on expanding operations in a new area of the site.

The company wants to speed up the process of opening Nechalacho’s Tardiff deposit for extraction.

Tardiff is separate from the deposit currently being mined, which is billed as a small-scale “demonstration” of the rare earth minerals available at Nechalacho. By contrast, Vital says Tardiff is a “world class” deposit.

Tardiff “has the potential to anchor what we believe will ultimately be a globally significant producer of rare earth minerals,” Vital stated in a press release just before Christmas.

On Monday, Crookes said the latest round of drilling at Tardiff had begun and the company’s plan to focus on that deposit remained in place.

“I thank John for his leadership during his time in the role and wish him well in his next endeavours,” Crookes said of Dorward.

PUBLIC SERVICE 

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Why does time change when traveling close to the speed of light? A physicist explains

Time gets a little strange as you approach the speed of light.

Published: March 20, 2023 



Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com.


Why does time change when traveling close to the speed of light? – Timothy, age 11, Shoreview, Minnesota

Imagine you’re in a car driving across the country watching the landscape. A tree in the distance gets closer to your car, passes right by you, then moves off again in the distance behind you.

Of course, you know that tree isn’t actually getting up and walking toward or away from you. It’s you in the car who’s moving toward the tree. The tree is moving only in comparison, or relative, to you – that’s what we physicists call relativity. If you had a friend standing by the tree, they would see you moving toward them at the same speed that you see them moving toward you.

In his 1632 book “Dialogue Concerning the Two Chief World Systems,” the astronomer Galileo Galilei first described the principle of relativity – the idea that the universe should behave the same way at all times, even if two people experience an event differently because one is moving in respect to the other.

If you are in a car and toss a ball up in the air, the physical laws acting on it, such as the force of gravity, should be the same as the ones acting on an observer watching from the side of the road. However, while you see the ball as moving up and back down, someone on the side of the road will see it moving toward or away from them as well as up and down.

Special relativity and the speed of light

Albert Einstein much later proposed the idea of what’s now known as special relativity to explain some confusing observations that didn’t have an intuitive explanation at the time. Einstein used the work of many physicists and astronomers in the late 1800s to put together his theory in 1905, starting with two key ingredients: the principle of relativity and the strange observation that the speed of light is the same for every observer and nothing can move faster. Everyone measuring the speed of light will get the same result, no matter where they are or how fast they are moving.

Let’s say you’re in the car driving at 60 miles per hour and your friend is standing by the tree. When they throw a ball toward you at a speed of what they perceive to be 60 miles per hour, you might logically think that you would observe your friend and the tree moving toward you at 60 miles per hour and the ball moving toward you at 120 miles per hour. While that’s really close to the correct value, it’s actually slightly wrong.
The experience of time is dependent on motion.

This discrepancy between what you might expect by adding the two numbers and the true answer grows as one or both of you move closer to the speed of light. If you were traveling in a rocket moving at 75% of the speed of light and your friend throws the ball at the same speed, you would not see the ball moving toward you at 150% of the speed of light. This is because nothing can move faster than light – the ball would still appear to be moving toward you at less than the speed of light. While this all may seem very strange, there is lots of experimental evidence to back up these observations.

Time dilation and the twin paradox

Speed is not the only factor that changes relative to who is making the observation. Another consequence of relativity is the concept of time dilation, whereby people measure different amounts of time passing depending on how fast they move relative to one another.

Each person experiences time normally relative to themselves. But the person moving faster experiences less time passing for them than the person moving slower. It’s only when they reconnect and compare their watches that they realize that one watch says less time has passed while the other says more.

This leads to one of the strangest results of relativity – the twin paradox, which says that if one of a pair of twins makes a trip into space on a high-speed rocket, they will return to Earth to find their twin has aged faster than they have. It’s important to note that time behaves “normally” as perceived by each twin (exactly as you are experiencing time now), even if their measurements disagree.

The twin paradox isn’t actually a paradox.

You might be wondering: If each twin sees themselves as stationary and the other as moving toward them, wouldn’t they each measure the other as aging faster? The answer is no, because they can’t both be older relative to the other twin.

The twin on the spaceship is not only moving at a particular speed where the frame of references stay the same but also accelerating compared with the twin on Earth. Unlike speeds that are relative to the observer, accelerations are absolute. If you step on a scale, the weight you are measuring is actually your acceleration due to gravity. This measurement stays the same regardless of the speed at which the Earth is moving through the solar system, or the solar system is moving through the galaxy or the galaxy through the universe.

Neither twin experiences any strangeness with their watches as one moves closer to the speed of light – they both experience time as normally as you or I do. It’s only when they meet up and compare their observations that they will see a difference – one that is perfectly defined by the mathematics of relativity.

AuthorMichael Lam

Assistant Professor of Physics and Astronomy, Rochester Institute of Technology
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Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Two moons of Uranus may have active subsurface oceans

By Robert Lea 

The Uranus system may be even more interesting than we thought.

An illustration of Uranus and its five largest moons, Miranda, Ariel, Umbriel, Titania and Oberon. (Image credit: NASA/Johns Hopkins APL/Mike Yakovlev)

Two of Uranus' moons may have active oceans that are pumping material into space, a new study finds.


The realization that there may be more happening in the Uranus system than previously believed came via the discovery of strange features in radiation data collected by NASA's Voyager 2 spacecraft as it passed the planet almost four decades ago.

The new findings, concerning the moons Ariel and Miranda, also support the idea that Uranus' five largest satellites could have subsurface oceans, a notion suggested by Voyager 2 flyby observations.

Related: Photos of Uranus, the tilted giant planet

An image of Uranus taken by NASA's Voyager 2 probe during its flyby of the ice giant on Jan. 14, 1986. (Image credit: NASA/JPL-Caltech)

The study team examined radiation and magnetic data collected by the spacecraft in 1986, long before it made its way out of the solar system.

The newly reported observations of Voyager 2 — currently the only spacecraft to have visited Uranus — showed that one or two of the ice giant's 27 known moons are adding plasma particles into the Uranus system. This detection came in the form of "trapped" energetic particles the spacecraft spotted as it departed the ice giant.

The mechanism by which Miranda and/or Ariel may be doing this is currently unknown, but there is one very tantalizing possible cause: One or both of the icy moons may possess a liquid ocean beneath their frozen surface that's actively blasting plumes of material into space.

Similar particle-releasing moons exist around Uranus' fellow solar system ice giant Neptune and the gas giants Jupiter and Saturn. In the case of the Jupiter moon Europa and Saturn's Enceladus, it was the examination of particle and magnetic field data that provided the first hints that these are ocean moons.

"It isn't uncommon that energetic particle measurements are a forerunner to discovering an ocean world," study lead author Ian Cohen, a space scientist at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, said in a statement(opens in new tab).

"We've been making this case for a few years now, that energetic particle and electromagnetic field measurements are important not just for understanding the space environment but also for contributing to the grander planetary science investigation," Cohen added. "Turns out that can even be the case for data that are older than I am. It just goes to show how valuable it can be to go to a system and explore it first-hand."

Related: Why scientists want NASA to send a flagship mission to Uranus

Another look at Uranus and its moons

The findings will only strengthen the desire of planetary scientists to send spacecraft back to Uranus and Neptune to collect more data, which led to the suggestion of a $4.2 billion flagship mission to Uranus as NASA's next major planetary mission.

This mission wouldn't be ready to launch until the early 2030s, so in the meantime, researchers have been diving back into old data collected during the Voyager 2 flyby to make new discoveries.

The data examined by Cohen and the team was collected by the APL-built Low-Energy Charged Particle (LECP) instrument on Voyager 2, which characterized the population of trapped particles.

"What was interesting was that these particles were so extremely confined near Uranus' magnetic equator," Cohen said. He explained that this is strange because magnetic waves within the system would normally cause the particles to spread out, but these were cramped together near the planet's equator, between Ariel and Miranda.

The team had to eliminate the possibility that the crowded particles detected by Voyager 2 could be the result of the spacecraft flying through a chance plasma stream from the tail of Uranus' magnetosphere. They determined that, were this the case, the feature would have a broader spread of particles than were spotted by Voyager 2, thus allowing them to rule this out as an explanation for the unusual data feature.

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Cohen and the team then began to explore simple physical models, using knowledge about ocean moons developed and acquired since Voyager 2 made its Uranus flyby 37 years ago to recreate the data collected by the spacecraft. This indicated to them that the feature could have come only from a strong and consistent source of particles, with a specific mechanism to energize them.

They ruled out other possible explanations, arriving at the theory that the trapped particles come from at least one of Uranus' moons, with Ariel and/or Miranda being the leading suspects. The team thinks that the particles were ejected in the form of a vapor plume similar to those seen erupting from Enceladus. Another possible ejection mechanism is "sputtering," a process in which high-energy particles collide with a surface, triggering the ejection of other particles into space.

"Right now, it's about 50-50 whether it's just one or the other," Cohen said, referring to the plume and sputtering hypotheses.

Whichever ejection mechanism is at work in the Uranus system, the mechanism that gives these particles their energy is pretty much the same.

This energizing mechanism is likely to be a constant stream of particles flowing from the moons into space, generating electromagnetic waves. These waves then accelerate a small fraction of these particles to energy great enough to be detected by the LCEP instrument. This process would also keep the particles trapped and thus tightly confined, just as Voyager 2 saw.

More data would need to be collected from the region around Uranus before scientists could conclusively determine that the particles come from subsurface oceans on Ariel and/or Miranda.

"The data are consistent with the very exciting potential of there being an active ocean moon there," Cohen concluded. "We can always do more comprehensive modeling, but until we have new data, the conclusion will always be limited."

The team's results(opens in new tab) were presented at the 54th annual Lunar and Planetary Science Conference on March 16 and have been accepted for publication in the journal Geophysical Research Letters.

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