General science thread

Quote: Mission146

I watched a Neil deGrasse Tyson Science Talk video a week or so ago in which he discussed theoretical time travel.

I've read several times that if time travel were possible you would only be able to travel to the future and not to the past. The past is gone, it's done. The future has yet to happen. So even if you could travel to the future you couldn't come back. This is why we have never seen any time travelers, they can't go back to the past. This thing about the future and the past all existing at the same time is just twaddle.

Quote: Evenbob

I've read several times that if time travel were possible you would only be able to travel to the future and not to the past. The past is gone, it's done. The future has yet to happen. So even if you could travel to the future you couldn't come back. This is why we have never seen any time travelers, they can't go back to the past. This thing about the future and the past all existing at the same time is just twaddle.

I have a very limited understanding of astrophysics, spacetime and quantum mechanics, but based on what little I do think I understand, I tend to agree with you.

Those who think that travel to the past is possible at all tend to view time as an entity unto itself, but it's not its own separate entity and time is simply a measurement that mostly just describes how physical interstellar bodies relate to one another. More than anything, spacetime describes movement and energy, which is what makes travel to the future theoretically possible if only a body could just move quickly enough...of course, that's assuming that there are no wormholes or other implements by which the need for speed exceeding the speed of light would be rendered unnecessary.

In order to travel to the past, a physical being would actually have to have negative speed. It would literally have to move backwards through spacetime, which is impossible because, as you succinctly put it, "The past is gone, it's done," which to say what has happened has happened. As some theoretical discussions have also pointed out, even if one has traveled into the past, then the event of them traveling to the past has ITSELF already happened, which is why nothing about the past can be changed.

Of course, people can get into the theories of multiple dimensions and/or infinite Universes by which all theoretically possible causal and effect relationships have happened and are always happening, but damn, you've got to make some serious assumptions before that even becomes a possibility.

I think it's really equivalent to a belief in God when you get into theories of multiple existences and dimensions---humanity is just inclined to believe that it's much more significant, in the Universal sense, than it likely probably is.

God or no God, the Universe is mostly indifferent to our existence. It will remain so even when we are gone.

The past does not really exist as a place we can physically go to. The past is just a memory of what used to be the present. You can capture light from the present with a camera but that is not the past you are looking at. It's what the camera captured at that particular moment. It is a tiny representation of what used to be the present. We are fascinated by the past because we cannot change it. All we can change is the future. It's fun to think about the past and look at pictures of it in videos and movies. But it's a human trait, animals live totally in the present they do not sit around and pine for the past.

time slows as an object gets close to the speed of light, and stops as it reaches the speed of light if that were possible, so the theory in science fiction has been that if you go faster than the speed of light, time would go backwards. But that is a fictional theory and the scientific theory is that nothing [except electromagnetic waves of some kind] can reach the speed of light, and nothing can go faster.

in quantum theory and I think maybe observation, there is time travel possibility, see next

Quote: Carl Sagan tries to dumb it down for us

One of the basic ideas of how to do it is that there are fantastically minute wormholes that are forming and decaying all the time at the quantum level, and the idea is to grab one of those and keep it permanently open.

and, I think, make it large instead of 'fantastically small'

https://www.pbs.org/wgbh/nova/time/sagan.html

he also mentions the astronaut who gets so close to the speed of light that time really slows down bigtime. When he returns to Earth, everybody he knew is now dead etc. So in a sense that is time travel to the future.

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Researchers from three universities in Germany have created the coldest temperature ever recorded in a lab—38 trillionths of a degree warmer than absolute zero to be exact, according to their new work, recently published in the journal Physical Review Letters.

The breakthrough brings us one step closer to absolute zero, which could have huge implications for particle physics.

That's because the closer we get to absolute zero—the lowest possible temperature that we could ever theoretically reach, as outlined by the laws of thermodynamics—the more peculiarly particles, and therefore substances, act. Liquid helium, for instance, becomes a "superfluid" at significantly low temperatures, meaning that it flows without any resistance from friction. Nitrogen freezes at -210 degrees Celsius. At cool enough temperatures, some particles even take on wave-like characteristics.

Absolute zero is equal to −273.15 degrees Celsius, or -459.67 degrees Fahrenheit, but most commonly, it's measured as 0 Kelvins. This is the point at which "the fundamental particles of nature have minimal vibrational motion," according to ScienceDaily. However, it's impossible for scientists to create absolute zero conditions in the lab.

https://www.microsoftnewskids.com/en-us/kids/science-tech/scientists-just-created-the-coldest-temperature-ever-recorded-in-the-lab/ar-AAPdjkX?ocid=msedgntp

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one step closer to absolute zero ... However, it's impossible for scientists to create absolute zero conditions in the lab.

LOL

oh well, a site for kids

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NASA announced it’s going to crash a spacecraft into an asteroid's moon in an attempt to change its trajectory.

The mission - named "Double Asteroid Redirection Test"- will test whether NASA can redirect an asteroid if it is headed for Earth. NASA said it’s the first demonstration of the “kinetic impactor technique,” where scientists crash a large, high-speed aircraft into an asteroid to change its movement.

Bing Quock with the Morrison Planetarium at the California Academy of Sciences told KNX 1070 it's unclear if this mission will work.

“…because there are a lot of other things we need to be sure of,” he said. “One is what the asteroid is made of, how dense is it? Is it solid rock or is it a pile of rubble? How fast is it moving?”

Although there’s no current threat of an asteroid hitting the Earth, officials say “DART” will launch on Nov. 23.

https://www.science-for-old-codgers.com

This must be some of that "communism" experimentation. Thankfully they did more than point to more ice to conclude other evidence is potentially wrong.

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The natural experiment compared two similar labour markets, on either side of the border, to show what impact the increase in the minimum wage had in New Jersey.(Source: Johan Jarnestad/The Royal Swedish Academy of Sciences)

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So, they surveyed 410 fast food restaurants in New Jersey and Pennsylvania before and after the rise in the minimum wage.

And what they found challenged the economic orthodoxy.

"How do employers in a low-wage labour market respond to an increase in the minimum wage?" they asked in their 1993 paper.

"The prediction from conventional economic theory is unambiguous: a rise in the minimum wage leads profit-maximizing employers to cut employment."

They pointed to this 1946 paper by George Stigler as an example of the reigning economic orthodoxy.

"Our empirical findings challenge the prediction that a rise in the minimum [wage] reduces employment," they said.

"Relative to stores in Pennsylvania, fast food restaurants in New Jersey increased employment by 13 per cent."

And another interesting element of their research?

The rise in New Jersey's minimum wage occurred during a recession.

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Their research didn't conclude that an increase in the minimum wage would boost employment in every circumstance. Far from it.

But it challenged the view that an increase in the minimum wage would always lead to unemployment.

https://www.abc.net.au/news/2021-10-13/nobel-prize-in-economics-2021-david-card-minimum-wage/100531994