Search results

  1. Janus

    Can heavy objects be used to modulate light waves with small amplitude?

    Well, for one thing, static masses do not emit gravitational waves. You need something like masses orbiting each other to produce them. Gravitational waves are a secondary effect of gravity, in that you need gravity to have gravitational waves, but you don't need gravitational waves to have gravity.
  2. Janus

    Polarized Light -- Idea for headlight safety

    I have an old physics text, copyright 1936, which brings up the suggested idea of using polarization to reduce headlight glare. So, as you said, it is not a new idea. The fact that it never became common usage in the 80+ yrs since seems to speak to its practicality.
  3. Janus

    Does Gravity Deflect Light according to Newtonian Mechanics?

    The caveat here is the the the force causing the acceleration is $$ F_g = \frac{GMm}{r^2}$$ thus we can argue that since acceleration is F/m, the acceleration of m is $$ a_g = \frac{GM}{r^2} $$ and Ag is independent of the value of m. However, if m=0 then $$ F_g = \frac{GM(0)}{r^2} = 0 $$ and...
  4. Janus

    Bent light across the sea

    There is always some refraction due to the atmosphere that causes light to bend in its path and allows you to see a bit beyond the physical horizon. This effect can be increased when there is a temperature gradient in the air, such as when warm air is sitting over a cool body of water. In...
  5. Janus

    Why the Frequency of Light Does Not Change Through a Medium

    The front end of wave 2 leaves the emitter 1 sec after the the front of wave 1. The light travels at c in a vacuum until it hits a medium where the speed at which the light travels is 1/2 c. If we assume that the width of this medium is 1 light sec then when the front of wave 1 will take 2...
  6. Janus

    Speed of light times 2

    The problem with this type of argument, is that if we assume that we have a light bulb that can travel at c we are assuming something that is forbidden by the rules that make up our present understanding of the universe. This means we have to abandon those rules. But if we do this, we have...
  7. Janus

    Light in a cup (Can you explain this phenomenon?)

    Here's a quick render of light reflected from the inner side of a semi-circle. You can get some really pretty patterns just by reflecting light off of curved surfaces
  8. Janus

    Question about suborbital flight and ballistic missiles

    Then using the 1200 km apogee and the 6372 km semi-major axis, we get a velocity of ~6.5 km/s at apogee.
  9. Janus

    Speed of light, permeability and permitivity of free space

    No, the permeability is the constant that relates (in the example) the current to the strength of the magnetic field. In essence, it is the constant that determines the strength of a the field at any given distance from a magnetic pole. A changing electric field produces a changing...
  10. Janus

    Does doppler effect affect ENERGY of photon?

    There is no such thing as the INTRINSIC frequency of a photon. The energy of the photon is frame dependent. The energy of a photon and thus its frequency as measured by someone at rest with respect to the source will be different than that it would be for some one moving with respect to the...
  11. Janus

    The effect of Earth's Roatation on Flight

    You would move with it because you are already moving with it. Even if you remove the air from the equation, Lifting yourself from the surface of the Earth will not change your velocity with respect to the surface. If you are standing at the equator, the Earth is moving West to East at ~1000...
  12. Janus

    Faster than the speed of light paradox

    Wrong. The tap would travel through the stick at the speed of sound for the material that the stick is made from, and the speed of sound through any material will always be less than the speed of light.
  13. Janus

    Naive question about the speed of light

    The point is that according to Maxwell's equations, if you could move at a different speed than c relative to a light beam(as measured by you), then for you, the electromagnetic wave that the light consists of would vanish. The practical result of this would be that unless you were perfectly...
  14. Janus

    Why is light affected by gravity?

    To be more accurate, gravity interacts with the stress-energy tensor.
  15. Janus

    Other Special Speeds? (than light)

    There can only be one invariant speed. The invariance of c results in it being the "speed limit" for the Universe. Speeds greater than c don't exist, so you can't have any invariant speed greater than it, and if you had an invariant speed less than c, then it would be the speed limit of the...
  16. Janus

    Light powered spaceship

    You have to keep in mind that this is a theoretical maximum. It doesn't factor in how much of the energy is wasted, or used to maintain the containment system needed for the antimatter or even how massive a containment system for that much antimatter would be. The vast majority of that 10000 kg...
  17. Janus

    Light powered spaceship

    I finally found an article that describes the system. Basically, it is a modified light-sail concept. The gain comes from bouncing the light back and forth between the spacecraft and launch platform, rather than just once as in the case of the light sail. It isn't "take your engine with...
  18. Janus

    Light powered spaceship

    Using the relativistic rocket equation, it works to about 0.46c. This is assuming that all of the energy can be directed as light propelling the craft. No, it wouldn't reduce the amount of matter needed. What determines that is the "exhaust velocity", which in this case is the speed of...
  19. Janus

    Light and Vision: Photon Direction

    That's what the lens of the eye is for. It converges the light from each point source to a single point on the retina.
  20. Janus

    Faster than light Information Possible?

    Once the light leaves the laser it is no longer effected by anything the laser does after that. When you move the laser, the light that left it before that moment continues along in the same direction as it was before you moved the laser. The whole length of the beam will not move, just that...
  21. Janus

    Traveling .999999 reapeating the speed of light .

    You can't travel at 0.999999999... c, but you can travel at 0.99999999...9c, where in the first case the ... means an unending string of 9s, and the in the second it means a finite but undetermined number of 9s.
  22. Janus

    Speed of light

    The speed of light in a vacuum is invariant. It is measured to be the same by everyone regardless of their relative motion. For example, a beam of light traveling past the Earth will have a measured relative velocity of 3e8 m/s wrt to the Earth as measured by the Earth, but an observer flying...
  23. Janus

    Estimate the power of the laser on board of Darth Vader's Death Star

    Interesting that that number works out to very close to the gravitational binding energy of the Earth (2.24*10^32 J)
  24. Janus

    Newbie question: Why is the speed-of-light squared equal to energy/mass?

    To start off, c isn't just the speed limit for light, it is the speed limit for everything. What is so special about c is that it is a speed that everyone measures as the same relative to themselves. For instance if you turn on a flashlight you will measure that the photons leaving the light...
  25. Janus

    Settle my dispute- Can you see more of yourself in a mirror?

    As long as your image in the mirror fits in your field of vision, You will see the same amount of yourself in the mirror. It is only when you get close enough to the mirror that your image goes beyond your field of vision do you see less of yourself.
  26. Janus

    When bulb light passes through a prism

    Are you passing the light through a slit before it reaches the prism, or are you just holding the prism up to the light from a light bulb?
  27. Janus

    Faster than light?

    When you square something with physical units the answer will be in different units and you are not changing the original units. Example, assume you have a room that has walls of 10 ft length each. If I square the length of the walls, I get an answer of 100 square feet, a measure of area...
  28. Janus

    Faster than light?

    Meta Research is run by Tom Van Flandern, who is not a reputable source when it comes to such matters.
  29. Janus

    Laser Listening Device

    This was several years ago, late 80's or early 90's. The mag is out of print and the publisher went out of business in 2002. It probably wouldn't do you much good either as you would most likely not be able to get some the components anymore.
  30. Janus

    Laser Listening Device

    Several years ago, The magazine Radio Electronics had a project where you built such a laser eavesdropping device. You could do it all yourself or you could order some of the specialty items form them (the lasers and the etched pc boards/). I remember that they included the disclaimer to the...
Top