# All Activity

1. Past hour
2. ## Why Biotin Improves Hair Growth

Hi, I know that the vitamin biotin (B7) improves hair growth. What I wonder is why is this? One website states the following: ""The biotin you consume in foods helps your body to turn the food you eat (protein, carbohydrates, and fat) into energy.". How does it make the hair grow faster then?
3. ## Who said the Universe had a beginning?

Are you saying that the big-bang region of the universe (because we know nothing about the region beyond our visual horizon) may have existed for an infinite time in a strange state before changing at the moment the big bang began expanding?
4. ## U.S. Democratic Primary

Castro has made the Fall debates:
5. Today
6. ## Where to submit my proof that the set of real numbers can't be well ordered

If a set S is WO it has to have an element, m, such that S={x: m ≤*x} and this is not the same as S'= {x: a<*x, for some a}. I am saying there can always be an S'. This 'finite downward chain' was also part of my thinking, but I was really trying to show any z in T was also contained in my countable sequence of z's which might really be doable. The difference between S and S' should be sufficient though. If a set S is WO it has to have an element, m, such that S={x: m ≤*x} and this is not the same as S'= {x: a<*x, for some a}. I am saying there can always be an S'. This 'finite downward chain' was also part of my thinking, but I was really trying to show any z in T was also contained in my countable sequence of z's which might really be doable. The difference between S and S' should be sufficient though. For some m in S' how do we know there is an x in S' such that a<*x<*m? We would just have to look at the particular order relation, <*, to find it. We would have to find what we think is m too.
7. ## About life and consciousness.

You're setting the bar to your level of understanding. It's a little like trying to understand how and why the Egyptians built pyramids, when all we know is, they did... There is no line...
8. ## VARIPEND

Ok! I will simplify for you. Here is a brick, at rest. Nothing is pushing the brick, sum of external forces are zero. The brick is hollow. Hidden inside is a varipend, the device described by you. Will the brick accelerate due to the variepend that is active inside? You seem to claim, but avoid to answer, that you think that F=ma does not apply to your device* *) This is not the only physical laws that the description seems to break but one law at a time is enough.
9. ## About life and consciousness.

And what about the ability of abstract thoughts and a sense of mortality perhaps these are necessary attributes of consciousness or maybe I’m just setting the bar too high for what consciousness is.
10. ## VARIPEND

First off the CM cannot change direction without acceleration that is basic physics. Acceleration includes changes in direction so some force must be involved internal or external.
11. ## Water ice, sublimation, vacuum.

It has been discovered that there is water ice in the perpetually shaded craters on the Moon and on Mars. I have always understood the freeze-drying process to be an acceleration of the sublimation process of water when frozen and subjected to a vacuum. Therefore, I do not understand how there could be water ice on either the Moon or Mars. Why has not the ice on the Moon (and Mars, et. al.)sublimated and dissipated into space especially inasmuch as it has no atmosphere? The only reason I can think of for that not to happen is that there has to be some involvement with oxygen for sublimation to take place. An explanation, especially accompanied by a chemical formula that demonstrates the process of sublimation would be most welcome.
12. ## VARIPEND

For a brick, the unequivocal answer is NO! ${a_{c1}} = \frac{{\left[ {{m_1}{{\ddot r}_1}} \right]}}{{{m_1}}} = {{\ddot r}_1} = 0$ if ${{\vec F}^e} = 0$ For the CM system of bodies, the answer is YES! Acceleration of the Center of Mass is not a function of "external force." ${a_c} = \frac{{{d^2}{R_c}}}{{d{t^2}}} = \frac{{\sum {{m_i}{{\ddot r}_i}} }}{{\sum {{m_i}} }} + \frac{{\sum {{{\dot m}_i}{{\dot r}_i}} }}{{\sum {{m_i}} }} = ?$ if ${{\vec F}^e} = 0$ The acceleration of the CM of the system of bodies is the result of both external and internal forces. But the most interesting is another! The CM of a system of bodies can change without acceleration at all! You talk about CM, having in your head the concepts of "force", "acceleration", "velocity" ${{\vec R}_c}(t) = {{\vec R}_c}(0) + {{\vec V}_c}(t)t + \frac{1}{2}\frac{{{{\vec F}^e}}}{M}{t^2}$ But the CM "moves" like this: ${{\vec R}_c}(t) = \frac{{\sum {{m_i}(t){r_i}(t)} }}{{\sum {{m_i}} (t)}}$ The CM cannot move! CM is not a material object! A CM can only CHANGE how the result of a function of 2 (two) variables changes. I also have the right to ask you questions. Do you see the CM of this system? Do you see how he moves? === The Varipend task is not mathematically complicated and has a very accessible explanation from a physical point of view, which does not go beyond the school textbook. but this task is extremely difficult in terms of psychology. Therefore, I must ask you questions so that you LEARN to answer them YOURSELF.
13. ## VARIPEND

! Moderator Note Last chance. If you do not answer some of the questions asked in your next post, this thread will be closed.
14. ## VARIPEND

will show how the coordinates of the CM of the Varipend system are determined: ${r_c}(t) = \frac{{{m_{liquid}}(t){r_1}(t) + {m_{case}}(t){r_2}(t)}}{M}$ What is necessary and (or) enough to know in order to calculate the CM of this system at any given time? a) it is necessary to know the Law of Conservation of Momentum and on the basis of this law to calculate the coordinates and masses of parts of the system at any time? b) it is necessary to know the Law of Conservation of Energy and based on this law to calculate the coordinates and masses of parts of the system at any time? c) firmly enough to grammatically “know” how a brick behaves, which lies on the road in anticipation of external forces? Because it should be “obvious” to any dunce familiar with “twice two equals four”?
15. ## VARIPEND

! Moderator Note This thread is for you to explain your idea, therefore you should be answering questions not asking them. If this continues, this thread will be closed.
16. ## VARIPEND

Look﻿ carefully aga﻿in! The momentum of the moving substance changes The change in momentum is called "force." The force acts on the" body-case". If the "body-case" is freed from external retention, the "body-case" will move with acceleration! The change in the momentum of the "body-case", increasing its mass, will be equal to the change in the momentum of the moving mass. ================================================================ once more! ================================================================
17. ## VARIPEND

Try answering questions instead of posting new questions. What will happen according to you? Will there be acceleration a>0 even if F=0?
18. ## VARIPEND

I did. I’m trying to understand what you are proposing. So I try to use words commonly used in scientific discussions. Put your rig inside a hollow sphere and call the complete assembly ”body” if that helps define an answer.﻿ Oh well! Look carefully again! Does the mass of the “body” change? On the “case”, does the “force” act? How will the “body-case” behave if it is allowed to move in its own way? What will the constant total momentum of this system look like in the absence of external forces?
19. ## VARIPEND

I did. I’m trying to understand what you are proposing. So I try to use words commonly used in scientific discussions. Put your rig inside a hollow sphere and call the complete assembly ”body” if that helps define an answer.
20. ## VARIPEND

Body?! Who said "BODY"? Look again carefully! What do you see?
21. ## VARIPEND

Ok. Let’s make sure we discuss the same thing. A body with mass=m is at rest in our frame of reference, in vacuum in free space. There are no external forces acting on the body; the sum of forces acting is = 0. According to Newton the equation F=ma describes the situation; how the object will accelerate. Since force F=0 then acceleration a=0. Are you claiming that you have found a way to make a body accelerate even when F=0?
22. ## VARIPEND

This force is equal to the change in the momentum of the moving substance moving along the trajectory. hM-m-m...... CENTER Mass of the body system is associated with the total momentum? How long ago? Can you write an equation to calculate the center of mass of a system of bodies? Can you write an equation that allows you to calculate the SUM MOMENTUM of all the bodies in the system? Can you write the equation of CHANGE in the total momentum of a system of bodies? Those. just differentiate the total momentum?
23. ## The solution of the Cosmological constant problem ?

Yes your showing you can calculate the critical mass/energy density. You can do the same with the critical density formula which leads to the Hubble parameter. However this formula isn't strictly the cosmological constant. Critical density has three contributors. Radiation matter and Lambda.
24. ## VARIPEND

Yes. I will ask again: what are the forces? No, if the momentum remained constant, the center of mass would not move. How do you get the ball to do what it does without external forces?
25. ## VARIPEND

We’ll fix it right now! Although this is not an advertisement. Here is this system, in this form: The total momentum is LINK DELETED CHANGING ! This suggests that “external forces” act on this system in this form! If you release the system from external influences, then the LINK DELETED CONSTANT TOTAL MOMENTUM of this system will look like this: This is a simple solution to a First Order Differential Equation: ${p_{var}}(t) = {m_{liquid}}(t){{\vec v}_1}(t) + {m_{case}}(t){{\vec v}_2}(t) = 0$ ! pvar(t)=mliquid(t)v⃗ 1(t)+mcase(t)v⃗ 2(t)=0﻿ With a brick, everything is clear even to a schoolboy. More precisely, the student does not know anything except the brick! Now please change the momentum of the system of bodies. For example, brick systems! Such a system, where many, many bricks!
26. ## VARIPEND

I don't understand your objection. If I change the momentum of the brick, its velocity will change. Thus, velocity is an example of something that can change when there is an external force. And for a system of constant mass, it must change.
27. ## Synthesis of 1-cyclopentylpropan-1-amine from cyclopentene

Hello there! Can anyone please tell me how to theoretically synthetize 1-cyclopentylpropan-1-amine from cyclopentene in exactly 6 steps (no more, no less steps)? Thank you for all your answers!