« Last post by Eismail5 on Today at 04:44:29 »
I am hoping this is the correct area for this post.. And I apologize to the mods if it isn't!
So, my family had a giant clam Pearl that was found in the Philippines and now it is mine. I am trying to find how I can find a private seller, I do not want to do auctions at all and i am willing to negotiate the price
The Pearl is 17kilo , I don't have the length in front of me now but I have it.
It was tested in a lab in 2014 and I have the documents and I assume if I find a potential buyer they will want to get their own lab tests done.
I am in the USA and so is the Pearl (tri state area) .. I do not have the shell because it was way to big to travel with but I do have pictures of the Pearl and the shell.
I am not in this field and I don't know where to look for a buyer .. Would schools be interested? Are their institutions anyone knows of that purchases or may be interested in something like this?
If any one has any ideas where i should look it would help me so much .. I would like to sell it and since I am not in this field I do not have connections or guidelines where to find a buyer and I think it is something that someone or someplace would value..
Thank you !!
« Last post by Isak Bohman on Today at 02:54:40 »
This is correct. The sharpest peaks are the ones that remain a nunatak for a sufficient amount of time. You can clearly see this in eg Patagonia with Cerro Torre, or on Antarctica with eg Ulvetanna and surrounding mountains. Mountains that were located near the edge of an ice sheet were never completely covered in ice and their peaks remained intact while their sides got steeper. The results of this can be seen on eg Baffin Island, on Greenland and in Norway. The mountains farther inland are rounder and the ones closer to the coast are sharp. It must also be pointed out that the rock type must be right. The tallest and sharpest mountains in the world generally, predominantly consist of granite because this rock is extremely resistant to wear and contains very few cracks or other weaknesses compared to sedimentary or metamorphic rocks. Metamorphic rocks can also sustain sharp mountains but not as reliably. In the European Alps this is illustrated when we compare the Valais Alps with the Mont Blanc massif. Mont Blanc contains the most jagged peaks in the alps while the Valais Alps are almost as sharp, but not quite (Matterhorn is a very sharp peak in the Valais Alps, but there are other mountains in the Mont Blanc massif that rival or exceed this, eg Aiguille Noire de Peuterey, Petit Dru, Grandes Jorasses, Aiguille de la République or Dent du Géant). The Valais Alps are known for loose rocks while the Mont Blanc massif is a climber's mecca due to its rock quality -- thanks to the plutonic granite that contains few weaknesses and weathers mainly by breaking off in big chunks like the peels of an onion. Strong rocks don't break off as quickly when the glacier undercuts the face, allowing it to get steeper. If the rock type is too weak the mountain will get covered in glaciers and not steepen. Eg volcano summits (although this is caused by the the fact that volcanoes are not formed like regular mountains but instead are born with a certain steepness limited by the angle of repose; however, volcanoes also tend to be very weak which is why they generally can't be eroded to become very steep except for certain circumstances). Huge mountains such as Denali or those in the Himalayas cannot be made too steep without collapsing, regardless of rock type (FYI Denali is made out of granite but its sides are still of only modest slope due to the immense slope heights). We can see that the maximum average steepness of a mountain slope with a certain height decreases when we increase the face height, irrespective of rock type. The highest vertical faces in the world cap out at around a mile in height, eg Great Trango Tower. The highest walls in the world that can still clearly be labelled walls (steepness > 45 degrees) are those of Nanga Parbat (Rupal face), Dhaulagiri (W face) and Annapurna I south peak (SW face). They are each around 4500 m in height. There are clearly steeper walls at around 3000 m (Lhotse, Jannu or a subsection of the previously mentioned walls).
« Last post by Brad Watson on Today at 02:46:45 »
My apologies to the Chinese, I forgot...
The 12-year cycle of the Chinese zodiac is an approximation to the 11.86-year cycle of Jupiter, the largest planet of the solar system.
But it was in fact I who mentioned relativistic mass, and relativistic mass is clearly not wholly irrelevant to the current physics logic of how light moves across space, which is what I said I understood, and you said I didn't.
At no juncture have I said that relativistic mass causes redshift. I said that I understood the current physics logic of how light travels across space.
The relevant point is that gravity potential and relativistic mass have a direct correlation.
So what exactly are you saying? That I do understand, or that I don't? Because I'm not sure quite where you are coming from with this Trumpoid business, but I do recognise the word obtuse, and you are currently fitting this description...
You cannot seriously think that a cyclic universe can be described solely via the gravitational shift equation, nor legitimately purport the impression that current physics describes the logic of how light travels through space solely via the gravitational shift equation...
Physics, Astronomy & Cosmology / Re: How can the frequency of a clock in relative motion appear to decrease?« Last post by Janus on Today at 01:31:44 »
Later in that same article, he states the the clock postulate generalizes to General Relativity, which deals with gravity. General Relativity has time dilation without a difference in velocity. In the passage you quote, he is merely talking about how the Clock postulate applies to accelerating clocks in order to point out that the time dilation that you(in an inertial frame) measure for the clock is only related to the relative speed the clock has to you at that moment, and is independent of the magnitude of the acceleration it is undergoing at that moment.
5 km/sec is just too low a velocity for this type of exercise, in that to get any type of accurate answer you have to carry your calculations out to too many significant digits. For example, at 5 km/sec each, with A coming at you from the Right and B from the Left and you try to work out what velocity they have with respect to each other as measured by either, you need to use the addition of velocities equation. But if you plug those values in to a standard hand-held calculator, it will give you a result of 10 km/s, which is wrong (the correct answer is close to 9.9999999999999972 km/sec.) Now while my desktop calculator will handle this many decimals, it has only 1 memory cache. This means recording each intermediate result to use later and hoping you don't make a mistake somewhere along the line.
It is much better to use velocities where you don't have to carry things out to such a ridiculous number of decimals.
Thus, The same example with velocities of 0.25c gives an answer of 0.47c with the velocity addition theorem, a difference that is much easier to deal with. Also, such a scenario is much easier to work with in the form of Space-Time diagrams.
I am including the diagrams from the rest frame of the midpoint and the rest frames of both A and B with the 0.25c velocity( as measured from the midpoint)
First the rest frame of the midpoint
The circles mark the recorded times by SAC and SBC
The yellow lines represent the light carrying information about the reading of Clock A to Clock B and vice-versa. The "+"'s mark when either A or B records a particular tick from the other. In your set up you had SABC and SBAC starting when they get the signal from the midpoint. This does not really work because then neither records the first tick of the other clock until after the local clock has ticked of ~3, and then records the remaining ticks as arriving faster than the local clock. It makes more sense to have the length of the first tick as being recorded as the time between when the counter sees the light start the other clock. Then all the recorded ticks will be equally spaced.
You will note that all the counters will read the same time when A and B meet up.
Next we look at the rest frames of A and B (the left and right images below)
Please note that this is the exact same set up as the last image, just according to different inertial frames.
All three counters still read the same when they meet. The relative timing between seeing ticks from the other clock and their local clock is the same. However, the timing of the start of the clocks and their counters no longer match up. According to A, SBC starts counting before SAC does, and according to B, SAC starts counting before SBC. The same offset occurs for SABC and SBAC.
So even though Clock A ticks slower than Clock B according to Frame B, it starts ticking earlier and the clocks end up reading the same when they meet. In frame A, it is clock B that started earlier and runs slower, but you still end up with the same result.
« Last post by syhprum on Today at 01:00:57 »
The LIGO device only works because the gravity wave travels at c if it traveled faster the received frequency in the detector would have been higher and would not have corresponded to that calculated for merging black holes.
I think the designers of clockwork cars had all this worked out 100 years ago and abandoned their projects, this was before magical gearboxes were discovered with efficiencies of 10000%
PS the famous windup radios were quickly redesigned to incorporate batteries, the only success story for windup motors was for gramophone turntables where they were in use for about 80 years.
« Last post by evan_au on Today at 00:27:54 »
Quote from: OP
why are most mountain tops pointy?
On a recent tour of Canada and Alaska, our guide pointed out that there is a mix of "pointy" and "rounded" mountain tops in this part of the world.
The mountain chain on the west of Canada and USA is formed by the collision of tectonic plates, so the mountains are still actively growing (and eroding).
But the difference in shape is due to the depth of the ice sheet in the last ice age, which covered most of North America
- and, presumably the ice ages before the most recent one, too, although the most recent one has erased most information about previous ice ages.
- The ice sheet (and the boulders it carries) grinds away at the rock, rounding out the valleys and smoothing the mountain sides.
- If the mountain was tall enough to project above the ice sheet, the pointy top remains intact
- If the mountain was a bit shorter, and beneath the depth of the ice sheet, the pointy top is ground down to a more rounded shape.
- Getting up close to rocks exposed by recent glacial retreat showed deep gouge marks where boulders were scraped across the bedrock.
By the end of the tour, I could estimate the depth of the ice sheet by looking at the shapes of the mountain tops.
Quote from: evan_au
I suspect that the energy density would not be that great
There is enough on the geometry of the spring to estimate that the spring would take up a volume of 5 liters, have a unrolled length of 3m and a mass of 9.5kg (if I've done the calculations correctly!).
Assuming you always squashed the spring down as far as it would go (storing 3400J):
- The specific energy is around 360 J/kg, which is much less than:
- The rechargeable Lithium-ion battery in your smartphone, at around 500,000 J/kg.
- The non-renewable petroleum in your car, at around 46,000,000 J/kg.
- The energy density is around 660 J/liter, which is much less than:
- The Lithium-ion battery in your smartphone, at around 1,000,000 J/liter.
- Petroleum in your car, at around 34,000,000 J/liter.
Of course, the petroleum in you car is only half an energy source, and doesn't function at all without the oxygen in the air, which has far greater mass, and enormously greater volume than the liquid petrol in your "gas tank". And, naturally, a sink for the enormous volume of CO2 produced during combustion.
So I don't see this clockwork mechanism replacing electric (or petroleum-fueled) cars in the near future, nor solving our greenhouse gas emission problems.
Clockwork mechanisms should stay in their current niche in toy cars, where they are cheap and effective.
« Last post by alancalverd on 02/12/2016 23:34:05 »
A new term has been promulgated in Physics World this week: "trumpoid". It is a statement that has absolutely no basis in fact, but supports the speaker's argument by casting aspersions on the integrity of others. The test of a trumpoid is that, when challenged, the source says "I didn't mean that" or "so what if it isn't true?"
At no point did I mention the relativistic mass of a photon, because it is wholly irrelevant to the mechanism and quantity of redshift.
The value of relativistic mass is an effect, not a cause, of redshift.
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