Unraveling the Mysteries of Spacetime: How Physicists Know

In summary, physicists determine that spacetime was created at the big bang through observing the expansion of galaxies, rather than just their motion. This idea is supported by the violation of the first law of thermodynamics and the lack of a definitive center or collapse if only mass was created. Additionally, there is significant evidence pointing to a small, dense, and hot beginning of the universe.
  • #1
Jonnyb42
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How in the heck do physicists know that spacetime was created at the big bang just by observing galaxies moving away from each other? Couldn't that mean that that's when the MASS was created?
 
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  • #2
You made the classic mistake of thinking that it's motion of galaxies moving away from each other into existing space. It's not. It's not space was there, and boom stuff was created and now it's flying away from each other like an explosion. It's spacetime itsself that is expanding.

You idea that it could just be the mass that was created violates the 1st law of thermodynamics, which if the Universe was existing before hand follows the same phyical laws that govern us. Not only that, but if just the mass was created in the existing universe then there would be a definitive centre that could be found. Also if all the matter were created in 1 single spot, gravity would dominate and it would collapse back in on itsself.

Those are three of the big problem with the idea that it was just the 'stuff' that was created within the universe, not the universe itsself.

There are also many other peices of evidence that point to a small dense hot beginning to the universe.
 

1. What is spacetime?

Spacetime is a concept that combines the three dimensions of space and the dimension of time into a single framework. It is a fundamental part of Einstein's theory of relativity and is used to describe the physical world.

2. How do physicists study spacetime?

Physicists study spacetime through a combination of theoretical calculations and experimental observations. They use mathematics, such as calculus and geometry, to develop models and equations that describe the properties of spacetime. They also use tools like telescopes and particle accelerators to make observations and test their theories.

3. What are some key features of spacetime?

Some key features of spacetime include its curvature, which is affected by the presence of mass and energy, and its ability to be affected by gravity. It also has a constant speed of light and can be distorted by high speeds and strong gravitational forces.

4. How do we know that spacetime exists?

We know that spacetime exists through various experiments and observations that support the theories and equations developed by physicists. For example, the bending of light around massive objects, predicted by Einstein's theory of general relativity, has been observed and confirmed by multiple experiments.

5. What are some current mysteries surrounding spacetime?

Some current mysteries surrounding spacetime include the nature of dark matter and dark energy, which are thought to make up a large portion of the universe but have yet to be fully understood. Additionally, there are ongoing efforts to reconcile the theories of general relativity and quantum mechanics, as they currently have conflicting descriptions of spacetime at a very small scale.

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