Show Posts
This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.
I can remember receiving the oral polio vaccine in primary school. As I recall, it was a bright pink droplet on a small white spoon.I got it via sugar cube.
How big would a sattelite need to be in Low earth orbit (approx 250 miles) to appear to be the size of a postage stamp to the naked eye ?As big as a postage stamp at what distance from the eye? For example, the Full moon is about the "same size" as a quarter seen from a distance of 9 ft. A quarter three feet away will appear to be 3 times wider than a full Moon.
Which is why you had to use a AM radio (550-1720 khz) rather than FM( 88 - 108 mhz)* on those late nights.Quote from: Janus"skip" bouncing the signal between surface and ionosphereIonospheric skip propagation works with "shortwave" radio bands, up to around 30 MHz.
The old analog terrestrial TV used frequencies above 50MHz, which pass through the ionosphere out into space. They don't propagate past the curvature of the Earth,
Those ham radios took advantage of "skip" bouncing the signal between surface and ionosphere, which allows the signal to "bend" over the horizon.Unfortunately it doesn't clearly indicate the dish diameter (which is important to calculate antenna gain).If the packing peanuts at the bottom of the crate are "normal" than it's about 2 feet across.
Does that help?
For what it's worth, there are amateur TV transmitters- the equivalent of "ham radio" who get large ranges on low powers.
It's perfectly possible.
Take the sun and the earth (distance 8 light minutes). Let's say the time is 1:30 on earth, we see the sun at 1:22, moving at the speed of light, we just hit the sun at 1:30 (8min.),No. If it is 1:30 on the Earth, and we "see" 1:22 at the Sun, we know that it is 1:30 at the Sun, since the light we are now seeing from the Sun left it when both the Sun's and Earth's clock's read 1:22. If we Now travel to the Sun at c ( thus ignoring Relativity), it will take 8 min ( Earth and Sun time) to get there and we will arrive at the Sun at 1:38, while seeing 1:30 at the Earth (But knowing that it is actually 1:38 at the Earth.
Moving 8 times faster (for indicative and), we overcome this distance is only 1 minute and we get into the sun at 1:23, and since the distance between us and the earth is 8 holy minutes, we (if we could) see the earth at 1:15. If we go back to earth at the same speed, we will get home at 1:16, that is, in our past.You'd arrive at the Sun at 1:31, see the Earth at 1:23 (During your trip you would see the Earth clock tick backwards), But you would still say that it is 1:31 at the Earth. If you return to the Earth, you will arrive when it is 1:32 (two minutes after you left), and see the Sun read 1:24 ( have seen the Sun clock run backwards during your trip)
The question doesn't necessarily violate relativity, as we can, for the sake of argument, say that the observer is made of tachyons. Such particles have never been detected, but at least they avoid the "more than infinite energy" problem when going faster than light. That being said, tachyons travel back in time and length contraction makes distances negative. That's a bit difficult for me to wrap my head around when it comes to what a tachyonic observer should see.The problem with a "tachyonic observer" is that tachyons can't travel at anything less than c, And that includes as measured with respect to each other. Also, with tachyons, it takes a increase of energy to slow them down towards c, and if they lose energy, they speed up.
sorry, translated from french by googleA couple of things. While there is a lot of dark matter in the universe, it is spread out very thinly. For example, the total estimated dark matter in our Solar system amount to about the mass of a smaller asteroid, and this is spread out over the whole volume of the solar system. Also, the very nature of dark matter is such that, because it really only interacts strongly by gravity, it is hard to detect on the scale of a lab.
I am not a scientist, but I am passionate about science.
I have imagined some things and I would like to submit it to people who know to tell me if I am a little crazy or if it is possible. Sorry I'm not very good at writing texts or explaining my ideas.
I've seen a lot of videos that talk about dark matter, according to them for galaxies to interact as we see it, it would take dark matter to explain things that we observe.
I saw that there were projects out there to try to capture dark matter particles and that it was almost elusive because it was rare, but if there were a lot we would capture them more easily ?!
I thought to myself why not start from the idea that dark matter is not matter, but a kind of grid, like the grid lines on a sheet of paper. Which would act as a support to fix matter and dictate the physical laws of the universe.
Dark matter and dark energy would be one, they would only be the paper of the architect's plan, with its own physical laws. It would give the mass and energy properties to the particles. As if such and such a particle were a red pencil and another a blue pencil with each their characteristics
Perhaps this medium is intangible or energetic, it is a component of the universe that we do not yet know or that is not measurable.
It would be the thing that makes us speak of force of gravity, gravity would not really exist as an independent force but as a result of the laws of this support.
For example a black hole would be a kind of tearing of this support, creating a hole towards the non-universe where everything that falls in it dematerializes due to this non-grid of support.
What do you think, dear reader?
Armand.S
Galileo proposed a very simple reductio ad absurdam.And on a larger scale here:
Suppose a big rock falls faster than a small one. Now tie them together. The small one slows down the big one. But the big one accelerates the small one.
Torricelli is credited with demonstrating that a pebble and a feather fall at the same rate in a vacuum, and the experiment has been replicated on the moon.
Nope. In order to have an effect on the Earth's orbit, you have to eject something from the Earth at greater than escape velocity. (~11 km/s) A Tsar bomb at the bottom of the ocean would have its energy dissipated by the Ocean with none of it reaching escape velocity."If by mans activity during the hours of daylight (point of the earth facing the sun) applies force to the surface of the earth, whilst by the hours of darkness he is static, would this activity have an effect (however small) to permanently alter the distance of the earth from the sun"The detonation of a Tsar Bomb at the Mariana's trench, at the bottom of the pacific ocean would surely move the planet out of its current position...
No.
The laws of momentum conservation make this impossible.
Essentially, nothing on earth can change the earth's orbit, because it would have nothing to push against.
Needless to say, gigantic tsunamis would kill most of humans on the process witch given the facts is not entirely a bad thing...
Colin wants to know:The is increasing its period of rotation at a rate of 1.7 milliseconds per century ( every century it takes an additional 1.7 milliseconds to make one full rotation.)
Does this mean the Earth is slowing down? If so what are the consequences?
No. in order for rocket A to be able shut off its engine and still get rocket A into space is for it first to get rocket B up to the proper speed. If it cuts off its engine before that, gravity will just end up pulling rocket A back to Earth, and through the cable, rocket B back towards Earth.Rocket "a" pulls rocket "b", both on earth, with a shortish cable. If Rocket "a" is on space, apart from the extremely long chain/cable, would it be easier to pull rocket "b"? Would it save any fuel?Save fuel compared to What? Just rocket getting Rocket B in to space under its on power?.
In that case no. If the object is to get rocket B into space, there is no advantage to having it being towed by a rocket already in space. The only advantage the rocket in space has over the one on the ground is that its rocket engines would be slightly more efficient due to operating in a vacuum. But this isn't going to be much and it will be more than offset by the fact that Rocket A has its own mass on top of that of rocket A that has to be accelerated up to speed and that will take fuel even if you don't factor in any gravitational pull on rocket A by the Earth. And that's not counting the mass of the cable itself.
What I am curious about is this. The advantage of rocket A in space would be that once it reaches the power to lift rocket B, it can turn off the engine, lifting rocket B maybe even going at a snail pace. No?
Rocket "a" pulls rocket "b", both on earth, with a shortish cable. If Rocket "a" is on space, apart from the extremely long chain/cable, would it be easier to pull rocket "b"? Would it save any fuel?Save fuel compared to What? Just rocket getting Rocket B in to space under its on power?.
As Kryptid has also said, No, this is not frame dragging. Frame dragging is a GR effect that involves a rotating mass.It appears to me you switched the observers, who sees the light straight, no big deal.This is not frame dragging. This is just how the path of the light is judged as being as measured from different inertial frames.
No, frame dragging is a part of general relativity.
Why are you bringing this up here?
The frame dragging is part of the SR as per the figure.
The red arrow up stays 90 degree up in the train frame because it is dragged with the train frame from the platform point of view.
This is the fact.
Adding the aberration to this scenario.
If the platform observer wanted to send his own light along the right red line then the platform observer has to shoot the platform beam under an angle. That's the aberration.
These are the facts, I am not saying anything that is not in line with the SR.
If I am then please, show me,
Jano
Frame dragging is something totally different. To illustrate the difference, imagine the following scenario:
You have two observers above the pole of a rotating planet. One is inertial and the other shares the planet's rotation. A light beam comes in along the plane of Planet's equator.
First we will assume no frame dragging. From the inertial observer's frame the light comes in on a straight line until it hits the planet's equator. From the rotating observers frame, the light appears to follow a curved path. Again this is just due to the observations being made from different frames.
Now we add in frame dragging. The mass of the rotating planet adds a new factor to the space-time curvature. Now the Inertial observer will observe that the light follows a slight curve rather than a straight line, much like the rotating planet is trying to "drag" the light along with its rotation.
The rotating observer would note this too, but for him this "curve" is opposite to the curve he would have measured in the earlier example, so this results in his measuring slightly less of a curve in the light's path than he would without frame dragging.
Normally, frame dragging is a very weak effect. An exception to this is near black holes. With a rotating black hole, there can be a region ( the ergosphere) where the frame dragging is so strong that objects orbiting the black hole can only orbit in the same direction as the BH rotates.
Imaging two boys throwing a tennis ball across a moving train car.
Now they are doing the same thing on a moving open flatbed train car.
They throw the ball 90 degrees to the train velocity in the closed train car but under an angle on the open flatbed to account for the aberration.
So this is not frame dragging?
The tennis ball is not frame dragged inside the train car from the outside point of view?
I do not want to talk about light medium, just to point out that the observation about the light propagation appears to be similar to the one with the tennis balls.
Jano