scientific american - 1993 03 - black holes and the centrifugal force paradox
scientific american - 1993 03 - black holes and the centrifugal force paradox
... precess; the centrifugal force
on the spring must therefore be zero, and the total force equals
the gravitational force. The other craft travels at whatever
Copyright 1993 Scientific American, ... turn, equals
the sum of the two forces acting on the
weight: the gravitational force and the
centrifugal force.
To measure either one of these forc-
es alon...
scientific american - 1994 03 - visiting yourself in the past
... dam-
age. Our natural resources and the en-
vironment, now burdened by past pop-
ulation growth, will simply collapse un-
der the weight of this future demand.
The optimists, on the other hand,
comprising ... sublima-
tion) and then analyze everything that
comes out. Their results look quite a
bit diÝerent from those of their col-
leagues. A 35,000-year-old ice sample
from the G...
scientific american - 2001 12 - india, pakistan and the bomb
... limited
period (the 1980s and early 1990s) and a
limited number of states, it cannot be taken
as the last word on the subject. Neverthe-
less, it adds weight to the notion that tough-
on-crime policies ... 2001 Scientific American, Inc.
36 SCIENTIFIC AMERICAN DECEMBER 2001
BETTMANN/CORBIS
Profile
of the most-talked-about environmental issues of the
20th century.
The yea...
scientific american - 1993 09 - special issue - life, death, and the immune system
... oÝ and trav-
el to the cell surface. They serve as ripe
targets for the T cell, which can then
attack the infected cell and inhibit the
spread of the virus.
So far I have described T and B lym-
phocytes ... cells
mature in the thymus and in the bone
marrow, then circulate through the body
and lymphoid organs such as the spleen
and lymph nodes.
Copyright 1993 S...
the quantum physics of black holes and string theory
... 11-dimensional supergravity on a circle. The 11-dimensional theory has 5-
branes and 2-branes, and the 2-brane can end on the 5-brane. If we wrap on
the compact circle both the 5-brane and the ... 2-brane that ends on it, then in the
Type IIA theory we get a D4-brane and an open string ending on the D4-brane.
But if we do not wrap the 5-brane on the circle, and...
scientific american - 1993 01 - the turbulent birth of the milky way
...
declines as the reefs get farther away
from two centersÑone in the Indo-Pa-
ciÞc and the other in the Caribbean.
The outlines of a map marking plum-
meting diversity coincide with the con-
tours ... 4,400
12-BILLION-YEAR-
OLD AGE TRACK
15-BILLION-YEAR-
OLD AGE TRACK
NGC 288
NGC 362
Copyright 1992 Scientific American, Inc.
means that within the halo the only re-
maining m...
scientific american - 1993 04 - controlling the quantum jitters of atoms
... is
de-excited, and the cavity contains a photon (center). The atom
and the cavity continually exchange energy.
SCIENTIFIC AMERICAN April 1993 57
Copyright 1993 Scientific American, Inc.
April 1993 ... each oth-
er, and the other in which they swing
alternatively toward and away from
each other. The systemÕs oscillation in
each of these ÒeigenmodesÓ diÝers be-
ca...
scientific american - 1993 06 - tuning in the radio signals of ancient galaxies
... roughly the
same part of the chro-
mosome in SCID.
They decided to test
the hypothesis that defects in the gam-
ma-chain gene were causing the im-
munodeficiency. With the further assis-
tance ... they knew the precise rate of the cos-
mic expansion and the true geometry
of the universe, they could determine
to a similar precision the distance to the
galaxy and ther...
scientific american - 1993 10 - is los angeles winning the war on smog
... all the vehicles on
the road, the emissions-control equip-
ment was either removed by the own-
er or damaged by the use of leaded fu-
els. The latter problem has abated in
recent years as the ... cells incorpo-
rated the HS-tk gene, whereas virtually
no normal cells did. When they then
gave the rats ganciclovir, they got an-
other pleasant surprise. The drug killed
not onl...
scientific american - 1993 11 - reading the genes of extinct species
... Mexico and free
trade and against the U.S. and the wel-
fare of the dolphin. The U.S. had placed
an embargo on the import of Mexican
tuna on the grounds that the Þsh had
been caught in purse-seine ... in which the disease was inher-
ited along with the section of chromo-
28 SCIENTIFIC AMERICAN November 1993
cause damage or whether blame belongs
to the chemicals...
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