Ask a physicist anything. (8)

Subduction Zone · Jan 12, 2013

Worse yet, he figured a way to go directly downwind faster than the wind blowing him. It is easy to show iceboats that can tack back and forth and have a velocity made good course (average direction) that goes directly downwind faster than the wind. He made the first vehicle that was proven to go directly downwind faster than the wind. By about three times! There was a predecessor in this subject who may have gone downwind faster than the wind. His vehicle was good enough to convince the person he was arguing with that it could be done. He did not have the most modern of methods of measurement when he ran with his and it barely beat the wind, if it did at all.

Yes, I was terribly wrong about that subject. I actually learned a lot more because I was wrong than I would have on a subject that I already "knew".

Zippy the Wonderslug · Jan 12, 2013

I have a vague rememberance of the show of which you speak.
The analogy of the tuning fork caught my attention.
If I am remembering correctly, the theory for the communications was based on generating gravity waves at a set frequency. It was assumed that only the more advanced cultures would recognise these waves and would be capable of responding to them.
The use of quantum entanglement had not, at that time, been widely put forward and would require the use of particles from a single source to be moved from one location to others in order to operate properly. This could take several years before implimentation and would almost defeat the idea of instant communications.

I'm still crossing my fingers hoping that someone might recognize that TV broadcast I mentioned a few pages back.

I really, really would love to find it again.

Cheers.

Subduction Zone · Jan 12, 2013

Zippy the Wonderslug said:
I'm still crossing my fingers hoping that someone might recognize that TV broadcast I mentioned a few pages back.

I really, really would love to find it again.

Cheers.

I am unaware of the show that you are talking about.

Did you understand the following conversation in which it became obvious that quantum entanglement could not be used for faster than light communication?

Zippy the Wonderslug · Jan 12, 2013

^ Yeah, I understood it about as my simple brain could process.

I just would like to watch that show again if possible.

That's all.

Subduction Zone · Jan 12, 2013

mzungu said:
I came up with the same figures, so you are correct!

Apparently commercial satellites now offer resolutions at a lower price than their military counterparts and yes you are right; We have reached the limit of resolution.

Drones can do a better job and they are stealthy enough to go undetected in most cases.

However it is theoretically possible to use multiple satellites as one "telescope" and with image processing software to actually be able to resolve objects much smaller.

Too tired to delve further into this today. Have you seen the images from the Mars orbiter? Neat eh! Good night

I asked my friend about the GPS that he uses. Some of their units are used in NASCAR when they broadcast on TV. And the can get down to 2 cm. That is with a base station of known location and several satellites. Here is the part of the PM that covers this issue:

The answers can be complicated as you might imagine. I'll start with a bit of a simplification...

In normal mode (code phase) with nothing helping you out, you can achieve something on the order of 10 meters of absolute accuracy.

Then there's "differential mode". In this mode you place a receiver at a known location and have it communicate with the roving receiver. It measures its own position and compares the result to its known location. It then sends the error (or "corrections") to the roving receiver. This can result in an accuracy of about 1 meter absolute at the rover - by taking advantage of the low relative error and the known position of the base station. Corrections are usually sent on a satellite-by-satellite basis - rather than an X,Y,Z position correction.

Finally there's a mode called "carrier phase" in which the roving receiver basically counts or computes the number of actual wavelengths of the carrier signal from the satellite (not the data on that carrier) to compute an accuracy of about 2 cm. This also requires receiving base-station corrections, and it takes some time for the rover to resolve this accuracy. If the rover goes under an overpass and loses lock for even a second or two, it takes time to re-acquire again. In that sense it is not a robust solution. But there are ways to make it more robust (such as using an IMU to carry its position through brief outages).

In addition to these three methods, there are other related forms of corrections available. The WAAS satellites transmit corrections from ground stations so that a rover can approach differential GPS accuracy without any dedicated base-station or telemetry. Others have sent corrections from FM radio stations.

Oh and...

There are two frequency bands that can be used - L1 & L2. Almost all civilian receivers use L1 only. By using both frequencies you can compute some of the systematic errors (like refraction of the waves through the atmosphere) since the two frequencies are affected slightly differently. I don't recall what the numbers are when you look at L1/L2 with and without differential. I don't think it improves your accuracy significantly in differential or carrier-phase mode, but it does improve the robustness. In code phase I think it can improve your accuracy significantly.

This of course gives just the location.

So, there are ways of using GPS to get a very accurate location of an object this does not provide an image. So still no pictures of license plates from space.

grace24 · Feb 3, 2013

The big bang states all the matter was compressed into a tiny dot which triggers the big bang. According to the theory, it is not the beginning of the universe, but only a step forward in movement in space and time. This presupposes matter and space. You can't have the big bang without space and matter beforehand. How do you physicists explain this? Does M-theory explain this? Why do I still think the big bang brought in space and time? It's like which came first: the chicken or the egg. Are scientists stuck?

mzungu · Feb 3, 2013

grace24 said:
The big bang states all the matter was compressed into a tiny dot which triggers the big bang. According to the theory, it is not the beginning of the universe, but only a step forward in movement in space and time. This presupposes matter and space. You can't have the big bang without space and matter beforehand. How do you physicists explain this? Does M-theory explain this? Why do I still think the big bang brought in space and time? It's like which came first: the chicken or the egg. Are scientists stuck?

First of all the chicken came first. http://metro.co.uk/2010/07/13/the-chicken-came-first-not-the-egg-scientists-prove-447738/

As for the Big Bang; It was not an explosion. The term was coined by creationists and it stuck. We do not know what happened at zero time. We do know what happened after the "Big Bang" occurred. Give science time and I am certain eventually we will come up with the answer. This is the beauty of science; Scientists are not afraid to admit they do not know something.

grace24 · Feb 3, 2013

mzungu said:
First of all the chicken came first. 'The chicken came first, not the egg', scientists prove | Metro News

As for the Big Bang; It was not an explosion. The term was coined by creationists and it stuck. We do not know what happened at zero time. We do know what happened after the "Big Bang" occurred. Give science time and I am certain eventually we will come up with the answer. This is the beauty of science; Scientists are not afraid to admit they do not know something.

Yet, on the other hand, they say the big bang postulates the origin of space and time. You cannot have matter without space. Before the big bang there was nothing. There was no matter prior to the universe, matter came into being instantly at the moment of creation.

mzungu · Feb 4, 2013

grace24 said:
Yet, on the other hand, they say the big bang postulates the origin of space and time. You cannot have matter without space. Before the big bang there was nothing. There was no matter prior to the universe, matter came into being instantly at the moment of creation.

"Something" and "Nothing" are not meaningful concepts in Quantum mechanics. Matter does not come into being but rather is the transformation of energy into matter! What's your point; Are you implying that science should stop trying to understand the physical world and how it came to be Perhaps you would rather we revert back to the inquisition days when knowledge was accepted only if it served the purpose of religion and or warfare

Cactus Jack · Feb 4, 2013

How does NASA calculate the expense of putting a man on the moon (or Mars)?

mzungu · Feb 4, 2013

Cactus Jack said:
How does NASA calculate the expense of putting a man on the moon (or Mars)?

The same way any large corporation does in large projects. What is your point

AV1611VET · Feb 4, 2013

Cactus Jack said:
How does NASA calculate the expense of putting a man on the moon (or Mars)?

Probably used the lowest bidder.

Cactus Jack · Feb 4, 2013

Well, there are plots of land for sale on the moon, so I was figuring if I bought land up there I'd like to find a way getting there to use it.

grace24 · Feb 4, 2013

mzungu said:
"Something" and "Nothing" are not meaningful concepts in Quantum mechanics. Matter does not come into being but rather is the transformation of energy into matter! What's your point; Are you implying that science should stop trying to understand the physical world and how it came to be Perhaps you would rather we revert back to the inquisition days when knowledge was accepted only if it served the purpose of religion and or warfare

To me the big bang does not matter. To me the question is, where did the matter come from before the big bang? So they are appealing to matter and energy and time being eternal.That's only based on current observation. This is why cosmologists do not have a problem having a universe coming into being and first law of thermodynamics because it is a law of nature and do not govern prior to the creation of the universe.

The big bang was the beginning of space and time. They use philosophy/cosmology to explain, but the honest scientist admit that they have no naturally provable for it. They call it a singularity, which, by definition, is an event that seems to have taken place without any natural explanation. What I'm saying is they tied themselves in knots.

mzungu · Feb 4, 2013

grace24 said:
To me the big bang does not matter. To me the question is, where did the matter come from before the big bang? So they are appealing to matter and energy and time being eternal.That's only based on current observation. This is why cosmologists do not have a problem having a universe coming into being and first law of thermodynamics because it is a law of nature and do not govern prior to the creation of the universe.

The big bang was the beginning of space and time. They use philosophy/cosmology to explain, but the honest scientist admit that they have no naturally provable for it. They call it a singularity, which, by definition, is an event that seems to have taken place without any natural explanation. What I'm saying is they tied themselves in knots.

Ever heard of the Dirac equation!

Subduction Zone · Feb 4, 2013

grace24 said:
To me the big bang does not matter. To me the question is, where did the matter come from before the big bang? So they are appealing to matter and energy and time being eternal.That's only based on current observation. This is why cosmologists do not have a problem having a universe coming into being and first law of thermodynamics because it is a law of nature and do not govern prior to the creation of the universe.

The big bang was the beginning of space and time. They use philosophy/cosmology to explain, but the honest scientist admit that they have no naturally provable for it. They call it a singularity, which, by definition, is an event that seems to have taken place without any natural explanation. What I'm saying is they tied themselves in knots.

They do have an explanation for it. Go to YouTube and enter "A universe from nothing " by Lawrence Krauss. It is about an hour long lecture where Krauss explains how the universe could have come from nothing without breaking any laws of thermodynamics and the evidence that has been observed that supports this claim.

grace24 · Feb 4, 2013

Subduction Zone said:
They do have an explanation for it. Go to YouTube and enter "A universe from nothing " by Lawrence Krauss. It is about an hour long lecture where Krauss explains how the universe could have come from nothing without breaking any laws of thermodynamics and the evidence that has been observed that supports this claim.

Yes, I know this. But on the other hand, they say you cannot have the big bang without matter before hand. All of this required matter, time, and space. This is why you have M-theory.

They are stuck! Exactly my point. They don't know.

mzungu · Feb 5, 2013

grace24 said:
Yes, I know this. But on the other hand, they say you cannot have the big bang without matter before hand. All of this required matter, time, and space. This is why you have M-theory.

They are stuck! Exactly my point. They don't know.

Sometimes I wonder how far people will go to denounce science while at the same time enjoying the very fruits of science. In my opinion this is hypocrisy.

Why are you using the internet, computer, car, medicine, electricity, and a of amenities that you enjoy that are the fruits and labour of science.

I have reached my limit of trying to debate with people who belong in this category (creationists).

By the way the Flintstones were not real characters!

diychristian · Feb 13, 2013

OK I'm not crazy. Last night there was an AURORA type light in my bedroom.

My wife woke me up at about 6:20 or 6:30 said hey look at this (she's pregnant so i figured it was some weird mark on her body she wanted me to look out) I buried my face in the pillow and asked how was i suppose to see anything in the dark, she says no theres a light. I sit up and the entrance to our bathroom there's a flashing light (like the kids shoes that light up) i get out of bed to get a better look at it (i don't know what to do), so i approach it. My wife is flipping out. It was about 3ft off the ground eminating from near the middle hinge of our closet door. I'm within 5 ft of it. I thought I'll turn on the light and see whats causing it. I did and it disappeared. nothing was there. nothing reflective. no significant light source to reflect. the light was bright enough to reflect off cabinets 3ft away. i shut off the light and it hasn't come back.

What can cause such a thing? It's dry outside but not in the house (not enough for static electricity). I used some cleaners in the bathroom yesterday afternoon.

If it shows up again I'm touching the dang thing. Maybe I'll teleport or something.

Seriously whats happening?

Subduction Zone · Feb 13, 2013

grace24 said:
Yes, I know this. But on the other hand, they say you cannot have the big bang without matter before hand. All of this required matter, time, and space. This is why you have M-theory.

They are stuck! Exactly my point. They don't know.

I am not sure that mass is needed in the first place. Again, that part of physics is beyond my and I am sure your comfort zone. Once again, I suggest that you watch the video of Lawrence Krauss. He did not mention needing a seed mass as far as I can recall.

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