S2 special relativity Flashcards
What are the major ideas of special relativity?
Special relativity tells us that different observers can measure time, distance, and mass differently, even though everyone always agrees on the speed of light. It also tells us that no material object can reach or exceed the speed of light (in a vacuum) and that e=mc^2
What is relative about relativity?
The theory of relativity is based on the idea that all motion is relative. That is, there is no correct answer to the question of who or what is really moving in the universe, so motion can be described only for one object relative to another.
What is absolute about relativity?
All the predictions of the special theory of relativity follow from two assumptions, both of which have been experimentally verified: (1) The laws of nature are the same for everyone, and (2) the speed of light is the same for everyone.
What’s surprising about the absoluteness of the speed of light?
In our everyday lives, we expect velocities to add simply; for example, an observer on the ground should see a ball in an airplane traveling at the airplane’s speed plus the ball’s speed. However, this is not true for light, which everyone always measures as traveling at the same speed.
Why can’t we reach the speed of light?
Light always travels at the same speed, so your own light (the light that you emit or reflect) is always moving ahead of you at the speed of light. All other observers will also see your light moving at the speed of light—and because it is moving ahead of you, the observers will always conclude that you are moving slower than the speed of light.
How does relativity affect our view of time and space?
If you observe an object moving by you at high speed, you’ll find that its time is running more slowly than yours, its length is shorter than its length when at rest, and its mass is greater than its mass when at rest. Moreover, observers in different reference frames may disagree about whether two events are simultaneous and about the speeds of different objects.
Do the effects predicted by relativity really occur?
Experiments with light confirm that its speed is always the same. Experiments with subatomic particles in particle accelerators confirm the predictions of time dilation and mass increase at speeds close to the speed of light, and time dilation has also been verified at relatively low speeds. Nuclear power plants and nuclear bombs release energy in accordance with the formula e=mc^2 which is also a prediction of special relativity.
How can we make sense of relativity?
A person moving by you at high speed will see exactly the same effects on you as you see on her; for example, she’ll see your time running slowly while you see her time running slowly. Although this might sound contradictory, it simply tells us that time and space must be relative in much the same way that up and down are relative on Earth.
How does special relativity offer us a ticket to the stars?
Although the theory tells us that journeys to the stars will always take many years from the point of view of Earth, it also tells us that the time for the passengers will be much shorter if they travel at speeds close enough to the speed of light. Thus, the passengers may be able to make very distant journeys within their lifetimes, even though their friends back on Earth will not be there to greet them when they return.
