21

Technology / Re: Altering orbits using earth's magnetic field or generated fields from earth?

« on: 27/05/2020 23:43:59 »

How about the radiation fields ?

The Sun's radiation has been used experimentally to move spacecraft, with a solar sail:
https://en.wikipedia.org/wiki/Solar_sail

Cosmic rays carry a massive momentum for nucleus. However, they arrive randomly from all directions, so they are not very useful for controlled propulsion.

LEO (Low Earth Orbit) is shielded from most of the Sun's Solar wind by the Earth's magnetosphere. What remains is mostly low-density charged particles spiraling down the Earth's magnetic field lines towards the north & south magnetic poles. Since this doesn't provide a very consistent thrust to a satellite in orbit, it's hard to see how to use this for propulsion.
See: https://en.wikipedia.org/wiki/Magnetosphere#Earth's_magnetosphere

22

Technology / Re: Altering orbits using earth's magnetic field or generated fields from earth?

« on: 27/05/2020 22:35:24 »

I assume the energy you are hoping to create is due to your movement through the field ? This is a law of physics that escapes me at the minute but it had something to do with an airplane oving through the earths magnetic field and how much charge it would create its also constrained by energy conservation, basically you have to put energy in to the movement to get the electrical energy out.

Is it possible to use the earth's magnetic field to move around in space, or even take off from earth?

The earth’s magnetic field is very weak compared to the force required to move a spaceship. It can move a magnetised needle on a low friction support, but anything heavier like a bar magnet on a desk doesn’t move. Also even a weak bar magnet will easily overpower the earth’s field and influence a compass needle
As we get further from earth the earth’s magnetic field gets weaker, but a magnet will still be able to align along the field see

Notice how the magnet is stronger than the earth’s magnetic field.

How about the radiation fields ?

23

Technology / Re: Altering orbits using earth's magnetic field or generated fields from earth?

« on: 27/05/2020 11:48:34 »

Large satellites use gyroscopes to maintain their orientation in space.

Gyroscopes are a bit too heavy for tiny satellites, so small satellites in Low-Earth orbit generate a magnetic field, and work off the Earth's magnetic field (as illustrated by the astronaut).
- Unfortuantely, this won't give you propulsion, only orientation.
See: https://en.wikipedia.org/wiki/Magnetorquer
https://en.wikipedia.org/wiki/Control_moment_gyroscope

Is it possible to use the earth's magnetic field to move around in space

Yes, in a very limited way.

It has been suggested as a way to de-orbit old satellites in Low Earth Orbit, or to boost the orbit of satellites in Low-Earth Orbit, or even generate electricity in Low-Earth Orbit, using an electrodynamic tether.
- This has been tested from the Space Shuttle
- You don't get something for nothing; if you generate electricity, you lose orbital height; if you want to gain orbital height, you have to inject electricity
- I think the main concern is that a (say) 10km tether hanging in space would be a major obstacle to satellites in passing orbits. I think it would destroy too many satellites, and increase space shrapnel.
See: https://en.wikipedia.org/wiki/Space_tether

Is it possible to use the earth's magnetic field to ...take off from earth?

I can't see how this is possible - the Earth's magnetic field is too weak.

It is conceivable that a superconducting accelerator built in a vacuum tunnel up the side of a high mountain could launch satellites into orbit - but the mountain would need to be very high to get above most of Earth's atmosphere.

24

Technology / Re: Altering orbits using earth's magnetic field or generated fields from earth?

« on: 27/05/2020 07:10:12 »

Is it possible to use the earth's magnetic field to move around in space, or even take off from earth?

The earth’s magnetic field is very weak compared to the force required to move a spaceship. It can move a magnetised needle on a low friction support, but anything heavier like a bar magnet on a desk doesn’t move. Also even a weak bar magnet will easily overpower the earth’s field and influence a compass needle
As we get further from earth the earth’s magnetic field gets weaker, but a magnet will still be able to align along the field see

Notice how the magnet is stronger than the earth’s magnetic field.

25

COVID-19 / Re: Could the infection rate be significantly underestimated?

« on: 17/04/2020 16:19:00 »

It's highly likely that infection rates are higher than we thought or think. Partick Vallance (UK chief scientific officer) suggested at one point that the ratio of deaths to actual infections might be close to 1:1000; so with 10,000 plus deaths there may well have been 10 million cases in the UK already.

What will solve this is widescale serological testing. Once we can test the UK at scale for antibody to infection and discover how many people have really had it, we can refine and reinforce our models and control measures accordingly. Personally, I suspect that there has been considerable widescale spread in the community already.

26

COVID-19 / Re: Is viral pneumonia result of immune reaction or viral damage?

« on: 07/03/2020 22:36:19 »

Both.

Viruses are obligatory intracellular parasites, meaning that they rely on invading and hijacking our cells in order to replicate. When they do so, they usually compromise the cell, leading to its ultimate destruction. As such, viral infection leads directly to tissue damage; if this is in the lung, that's a pneumonia.

At the same time, viral replication in cells leads to the production of various cellular alarm signals called cytokines. These attract the immune system, which then sets about destroying virally-infected cells; but in the process it usually also causes bystander damage to adjacent healthy tissue. This is a pneumonitis.

Both phenomena will occur at the same time; usually the degree of damage is low, but in some cases it can be severe. The evidence we have is that the 1918 Spanish flu pandemic strain (H1N1) provoked just this sort of immune overdrive, leading to catastrophic lung damage, especially in people with healthy immune systems. This is, we believe, the main cause of death in these people.

27

Physics, Astronomy & Cosmology / Re: How microwave superheats water?

« on: 27/01/2020 09:20:58 »

Superheated water can be produced in pure water, in clean vessels without nucleation sites, and as long as it is not too agitated.
- So mechanical heating/stirring would not be a good way to do it
- Pure water is not very magnetic, so magnetic heating would not work so well
- Pure water is not very conductive, so heating by electric conduction would not work so well
- Inductive heating of a clean metal vessel could work
- Infra-red radiation (eg inside an oven) would work well

The information I gathered around this problem doesn't indicate the use of pure water.

The water can be regular drinking water but should not
contain many undissolved particles. It can be heated in any
domestic microwave oven; a research-grade microwave oven
such as used by Kennedy (1) to determine the enthalpy of
vaporization of liquids is unnecessary here. The recommended
heating vessel is a glass teapot sold to be used in the microwave
oven (no metal parts). Using such a teapot generally has several
advantages: its walls have relatively few nucleation
sites for bubble formation, yet enough to put a reasonable
limit on superheating; it has a plastic lid to prevent boiling
water from splashing out of it; and it has a plastic handle so
that it can easily be removed from the microwave oven once the
water is boiling.

Erné, B.H. & Snetsinger, P. (2000). Thermodynamics of water superheated in the microwave oven. Journal of Chemical Education
77(10), 1309-1310. doi: 10.1021/ed077p1309

And this is a comment by someone who can reproduce the phenomenon reliably.

Steven Spielman, PhD in Applied Physics; optical properties of solids
Updated Mar 4, 2019
I was able to accomplish superheating without much effort. I heated water in a small glass bowl, in a microwave oven. Before it reached boiling, tiny air bubbles adhered to the glass, the result of dissolved gases coming out of solution. When the boiling point was reached, (presuming here) water vapor entered these bubbles without bound and they grew quickly. The water boiled normally.

I shut off the microwave for a few seconds, and the boiling stopped. Then I turned it on again. The dissolved gases have already been driven out of the water, so there would have been no air bubbles to get things started. The water just sat there quietly for 10 seconds or so. Then there was a “PUNF!” sound. I opened the oven to find the bowl mostly empty and the walls and ceiling wet.

So, to avoid it, don’t microwave water (including coffee, etc.) which has recently boiled. Keep your face away when you first disturb it with a spoon or sugar.

https://www.quora.com/How-likely-and-how-dangerous-is-superheated-water-in-a-microwave-oven-and-what-everyday-precautions-should-be-used-to-avoid-injury

28

Physiology & Medicine / Re: Is the shingles vaccine still useful if I've recently had shingles?

« on: 01/10/2018 09:51:17 »

Shingles, also called zoster, is a manifestation of varicella zoster virus (VZV), which is a member of the herpesvirus family. These viruses characteristically infect for life, establishing a latent state from which they can later reactivate multiple times, producing a range of symptoms.

In the case of VZV (chicken pox) the primary infection, which is acquired through the air, produces a rash all over the body; this leads to the infection of sensory nerves that subsequently harbour the viral DNA for the lifetime of the infected individual.

Reactivation occurs from these nerve cells; in response to as-yet undefined signals the viral DNA switches on and begins to assemble new virus particles inside the nerve cell. These are exported down the nerve fibre to the overlying skin where they bud out and infect skin cells, producing infectious blisters.

We don't know why, but unlike the primary disease, the reactivation of chicken pox / VZV remains confined to one patch of skin called a dermatome. This region is supplied by one spinal nerve segment, so it may be that the reactivating virus in some way sends signals to the nearby nerves that all supply one body region and in this way promotes all of them to reactivate together.

The result is a strip of painfully-blistered skin; this is the syndrome referred to as shingles. The lesions are loaded with virus and highly infectious.

The virus is normally held in check - and these manifestations prevented - by the immune system, specifically by white blood cells called T cells. These can recognise when an infected cell begins to express viral chemical signatures that herald a reactivation and can kill the relevant cells. As a result, attempts by the virus to reactivate periodically are stamped out without you even realising.

This sub-clinically recurrent reactivation most probably has the effect of re-priming your immune response, encouraging the T cells to up their game and remain vigilant. It's called the Hope-Simpson model after the man who poposed it.

But as we age, or suffer intercurrent immune suppression or other chronic illnesses, the T cell population and the T cell response can dwindle. This can create a chink in the immunological armour, offering the virus an opportunity to break through and produce a shingles manifestation. Some people seem to be more susceptible to this than others.

Off the back of a reactivation, you will develop a much more profound immunity afterwards, but this will extinguish again over time and your vulnerability will return.

The vaccine contains a heavily-attenuated live VZV strain; injected into the muscle it undergoes limited replication but as it does so it displays the full genetic repertoire of the virus to the immune system, helping to re-kindle a comprehensive immune response. This increases the potency of your surveillance, reducing the likelihood of shingles.

Therefore, having the vaccine will reduce the risk of shingles in the near future; but having shingles will also reduce the risk of another attack of shingles in the near future, but probably not for as long as the vaccine because this will be given when you are well and able to make a more resilient immune response. By definition, when you have a shingles attack you are suffering an immune decrement, so this is not the best time to be making a long-lasting immune response.

I hope that answers the question for you.

29

Physiology & Medicine / During exercise, when does the body burn sugar and when does the body burn fat?

« on: 18/10/2005 06:06:29 »

Hi,
I heard on another PodCast that during the first 20 minutes of a cardiovascular workout, like running, the body is burning off only blood sugar. It is not unitl after the 20 minutes that you start actually burning fat. I don't know if this is true. However, if it is, does that mean that if you run in the morning before eating, that you burn fat sooner, since the blood sugar is probably lower?

I'd love to hear back from you. The show is great!

Thanks for all your knowledge.
From Minneapolis, MN with regards,

Leah Deal