Tagged Questions
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1answer
115 views
Why does Lorentz factor not hold for relativistic mass when we apply it to photons? [duplicate]
We know that the photon itself is massless particle $m_0=0$. But we also know, that the mass of the objects does increase with their energy. And we know that under certain circumstances (gravity, ...
1
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2answers
125 views
Relativistic Doppler effect derivation
This is about a step in a derivation of the expression for the relativistic Doppler effect.
Consider a source receding from an observer at a velocity $v$ along the line joining the two. Light is ...
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3answers
86 views
Special Relativity - speed of light question
Just a basic question:
I know that if you are traveling at $x$ speed the time will pass for you slower than to an observer that is relatively stopped. That's all just because a photon released at the ...
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2answers
106 views
If we are travelling with the speed of light, can we see what's behind us? [closed]
If we are travelling with the speed of light, can we see whats behind us(like if we are moving away from earth can we able see the earth)? And how we see the things that we are approaching with speed ...
3
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1answer
78 views
How would I perceive a purple ball when traveling at relativistic speeds
I have a 'thought experiment' which I'd like to ask about.
I was thinking what speed I would have to drive towards a crossing to see a red light as a green light - pretty easy, using the doppler ...
9
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2answers
698 views
Is the “How to break the speed of light” minute physics video wrong?
I am referring to this video, on YouTube, by minutephysics, which has quite a lot of views.
In the video it states that if you flick your wrist while pointing a laser that reaches the moon, that the ...
4
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4answers
719 views
What happens when a photon hits a mirror?
When a photon of light hits a mirror does the exact same photon of light bounce back or is it absorbed then one with the same properties emitted? If the same one is bounced back does it's velocity ...
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3answers
166 views
Does the Lorentz transformation not apply to light?
Since you would know that light always travels at the constant velocity with respect to all frame of reference ....according to relativity whenever we are traveling at speed of light our time with ...
1
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4answers
312 views
The speed of tachyons
The other day I was wondering: When a tachyon is coming towards you faster than the speed of light, will you see it before it hits you? Then I thought of course not, since the light waves aren't ...
1
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2answers
295 views
On Einstein's original paper: speed of light in different reference frames
On Einstein original paper "On the electrodynamics of moving bodies", on section 2 of the first part (Kinematics), the following thought experiment is described: a rod is imparted constant speed $v$ ...
2
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3answers
463 views
High speed and low speed photons
Looking at the discovery of the neutron, and I came across this page: http://www-outreach.phy.cam.ac.uk/camphy/neutron/neutron3_1.htm
The animation on the left, talks about low energy photons and ...
10
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5answers
105 views
How large is the universe?
We know that the age of the universe (or, at least the time since the Big Bang) is roughly 13.75 billion years. I have heard that the size of the universe is much larger than what we can see, in other ...
