True Wind

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Frequently Asked Questions...

According to present understanding, which of the following statements about the solar wind is not true?

A. It swept vast amounts of gas from the solar nebula into interstellar space.

B. It consists of charged particles blown off the surface of the Sun.

C. It is even stronger today than it was when the Sun was young.

D. It helped in the transfer of angular momentum from the young Sun to particles that blew into interstellar space, which explains why the Sun rotates so slowly today.


I think D on the basis of symmetry. (that is the flux is isotropic and would not led to a net change in angular momentum - there is no prefered direction)

Frictional forces probably slowed down the sun. Also, I believe A,B,C are true. But I am not an astronomer.

True Wind

True Wind Summit 2009 "Liquid"

Understanding Apparent Wind

Before you try and sail faster, you need to examine more closely the wind that hits your moving sailboat. The wind you feel on board your boat, when your boat is moving, is the apparent wind, which is different from true wind, or the wind felt by an anchored boat or a flag on shore.

To illustrate the difference between apparent and true wind, imagine jumping on a bicycle and pedaling down the road. If the day is calm, you feel wind in your face (apparent wind) — the faster you pedal, the more wind, right? And if the day is windy, the wind you feel in your face — your apparent wind — is the combination of the wind of motion, the wind blowing directly into your face that you create by pedaling fast, and the true wind, the wind blowing over the road.

The same phenomenon happens aboard a sailboat: As you move forward, you create a wind of motion that combines with the true wind blowing over the water, resulting in the wind you and your sails feel — the sailboat's apparent wind,

On very fast boats, this capability to "make your own wind" can have some really amazing results. For mortal monohull sailors, the difference between the apparent wind and the true wind is more subtle, except when you accelerate rapidly, such as when you catch a wave. Here are the key features of apparent wind:

The faster you go, the more effect your wind of motion has on the apparent wind's direction and velocity.

Apparent wind is always lighter (less velocity) when you're sailing away from the true wind than when you're sailing toward it. That's why sailing downwind feels warmer than sailing upwind.

Sailing straight downwind can be slower. Super speedy boats such as catamarans actually sail directly downwind (on a run) more slowly than if they head up and sail on a broad reach (deeper than perpendicular to the wind) and then jibe over.

Don't let apparent wind versus true wind confuse you; the sailor's universe still revolves around the wind that he feels. Just know that, as long as your boat is moving, the wind that you and your sails feel is technically called the apparent wind.

About the Author

woodchuck is an up and coming expert on crafts and hobbies. Do you want complete Push Block Plans? You can learn wood DIY Bench Stops plans, or you can learn woodworking by going to Push Stick Plans site.

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