<s>
The	O
Bolshoi	O
simulation	O
,	O
a	O
computer	B-Application
model	I-Application
of	O
the	O
universe	O
run	O
in	O
2010	O
on	O
the	O
Pleiades	B-Device
supercomputer	I-Device
at	O
the	O
NASA	O
Ames	O
Research	O
Center	O
,	O
was	O
the	O
most	O
accurate	O
cosmological	B-Algorithm
simulation	I-Algorithm
to	O
that	O
date	O
of	O
the	O
evolution	O
of	O
the	O
large-scale	O
structure	O
of	O
the	O
universe	O
.	O
</s>
<s>
"	O
The	O
principal	O
purpose	O
of	O
the	O
Bolshoi	O
simulation	O
is	O
to	O
compute	O
and	O
model	O
the	O
evolution	O
of	O
dark	B-Application
matter	I-Application
halos	O
,	O
thereby	O
rendering	O
the	O
invisible	O
visible	O
for	O
astronomers	O
to	O
study	O
,	O
and	O
to	O
predict	O
visible	O
structure	O
that	O
astronomers	O
can	O
seek	O
to	O
observe.	O
"	O
</s>
<s>
The	O
Bolshoi-Planck	O
simulation	O
,	O
with	O
the	O
same	O
resolution	O
as	O
Bolshoi	O
,	O
was	O
run	O
in	O
2013	O
on	O
the	O
Pleiades	B-Device
supercomputer	I-Device
using	O
the	O
Planck	O
satellite	O
team	O
's	O
cosmological	O
parameters	O
released	O
in	O
March	O
2013	O
.	O
</s>
<s>
A	O
successful	O
large-scale	O
simulation	O
of	O
the	O
evolution	O
of	O
galaxies	B-Application
,	O
with	O
results	O
consistent	O
with	O
what	O
is	O
actually	O
seen	O
by	O
astronomers	O
in	O
the	O
night	O
sky	O
,	O
provides	O
evidence	O
that	O
the	O
theoretical	O
underpinnings	O
of	O
the	O
models	O
employed	O
,	O
i.e.	O
,	O
the	O
supercomputer	O
implementations	O
ΛCDM	O
,	O
are	O
sound	O
bases	O
for	O
understanding	O
galactic	O
dynamics	O
and	O
the	O
history	O
of	O
the	O
universe	O
,	O
and	O
opens	O
avenues	O
to	O
further	O
research	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
they	O
led	O
to	O
some	O
predictions	O
,	O
for	O
example	O
about	O
the	O
distribution	O
of	O
galaxies	B-Application
,	O
that	O
do	O
not	O
match	O
very	O
well	O
with	O
observations	O
.	O
</s>
<s>
The	O
Bolshoi	O
simulation	O
follows	O
the	O
evolving	O
distribution	O
of	O
a	O
statistical	O
ensemble	O
of	O
8.6	O
billion	O
particles	O
of	O
dark	B-Application
matter	I-Application
,	O
each	O
of	O
which	O
represents	O
about	O
200	O
million	O
solar	O
masses	O
,	O
in	O
a	O
cube	O
of	O
3-dimensional	O
space	O
about	O
1	O
billion	O
light	O
years	O
on	O
edge	O
.	O
</s>
<s>
Dark	B-Application
matter	I-Application
and	O
dark	O
energy	O
dominate	O
the	O
evolution	O
of	O
the	O
cosmos	O
in	O
this	O
model	O
.	O
</s>
<s>
The	O
dynamics	O
are	O
modeled	O
with	O
the	O
ΛCDM	O
theory	O
and	O
Albert	O
Einstein	O
's	O
general	O
theory	O
of	O
relativity	O
,	O
with	O
the	O
model	O
including	O
cold	O
dark	B-Application
matter	I-Application
(	O
CDM	O
)	O
and	O
the	O
Λ	O
cosmological	O
constant	O
term	O
simulating	O
the	O
cosmic	O
acceleration	O
referred	O
to	O
as	O
dark	O
energy	O
.	O
</s>
<s>
The	O
first	O
100	O
million	O
years	O
(	O
Myr	O
)	O
or	O
so	O
of	O
the	O
evolution	O
of	O
the	O
universe	O
after	O
the	O
Big	B-Application
Bang	I-Application
can	O
be	O
derived	O
analytically	O
.	O
</s>
<s>
The	O
Bolshoi	O
simulation	O
was	O
started	O
at	O
redshift	B-Application
z	O
=	O
80	O
,	O
corresponding	O
to	O
about	O
20	O
Myr	O
after	O
the	O
Big	B-Application
Bang	I-Application
.	O
</s>
<s>
The	O
Bolshoi	O
simulation	O
employs	O
a	O
version	O
of	O
an	O
adaptive	B-Algorithm
mesh	I-Algorithm
refinement	I-Algorithm
(	O
AMR	O
)	O
algorithm	O
called	O
an	O
adaptive	O
refinement	O
tree	O
(	O
ART	O
)	O
,	O
in	O
which	O
a	O
cube	O
in	O
space	O
with	O
more	O
than	O
a	O
predefined	O
density	O
of	O
matter	O
is	O
recursively	O
divided	O
into	O
a	O
mesh	O
of	O
smaller	O
cubes	O
.	O
</s>
<s>
As	O
the	O
Bolshoi	O
simulation	O
ran	O
,	O
the	O
position	O
and	O
velocity	O
of	O
each	O
of	O
the	O
8.6	O
billion	O
particles	O
representing	O
dark	B-Application
matter	I-Application
was	O
recorded	O
in	O
180	O
snapshots	O
roughly	O
evenly	O
spaced	O
over	O
the	O
simulated	O
13.8-billion-year	O
run	O
on	O
the	O
Pleiades	B-Device
supercomputer	I-Device
.	O
</s>
<s>
Each	O
snapshot	O
was	O
then	O
analyzed	O
to	O
find	O
all	O
the	O
dark	B-Application
matter	I-Application
halos	O
and	O
the	O
properties	O
of	O
each	O
(	O
particle	O
membership	O
,	O
location	O
,	O
density	O
distribution	O
,	O
rotation	O
,	O
shape	O
,	O
etc	O
.	O
)	O
.	O
</s>
<s>
These	O
results	O
are	O
used	O
in	O
turn	O
to	O
predict	O
where	O
galaxies	B-Application
will	O
form	O
and	O
how	O
they	O
will	O
evolve	O
.	O
</s>
<s>
Starting	O
with	O
initial	O
conditions	O
based	O
on	O
the	O
known	O
distribution	O
of	O
matter	O
shortly	O
after	O
the	O
Big	B-Application
Bang	I-Application
,	O
and	O
using	O
Einstein	O
’s	O
general	O
theory	O
of	O
relativity	O
as	O
the	O
‘	O
rules’	O
of	O
the	O
simulation	O
,	O
Bolshoi	O
predicts	O
a	O
modern-day	O
universe	O
with	O
galaxies	B-Application
lining	O
up	O
into	O
hundred-million-light-year-long	O
filaments	O
that	O
surround	O
immense	O
voids	O
,	O
forming	O
a	O
cosmic	O
foam-like	O
structure	O
that	O
precisely	O
matches	O
the	O
cosmic	O
web	O
as	O
revealed	O
by	O
deep	O
galaxy	B-Application
studies	O
such	O
as	O
the	O
Sloan	O
Digital	O
Sky	O
Survey	O
.	O
</s>
<s>
To	O
achieve	O
such	O
a	O
close	O
match	O
,	O
Bolshoi	O
is	O
clearly	O
giving	O
cosmologists	O
a	O
fairly	O
accurate	O
picture	O
of	O
how	O
the	O
universe	O
actually	O
evolved.	O
”	O
The	O
Bolshoi	O
simulation	O
found	O
that	O
the	O
Sheth	O
–	O
Tormen	O
approximation	O
overpredicts	O
the	O
abundance	O
of	O
haloes	O
by	O
a	O
factor	O
of	O
for	O
redshifts	B-Application
.	O
</s>
<s>
This	O
research	O
was	O
supported	O
by	O
grants	O
from	O
NASA	O
and	O
NSF	O
to	O
Joel	O
Primack	O
and	O
Anatoly	O
Klypin	O
,	O
including	O
massive	O
grants	O
of	O
supercomputer	O
time	O
on	O
the	O
NASA	O
Advanced	O
Supercomputing	O
(	O
NAS	O
)	O
supercomputer	O
Pleiades	B-Device
at	O
NASA	O
Ames	O
Research	O
Center	O
.	O
</s>
<s>
The	O
Icelandic	O
singer-songwriter	O
Björk	O
used	O
footage	O
from	O
the	O
Bolshoi	B-Algorithm
cosmological	I-Algorithm
simulation	I-Algorithm
in	O
the	O
performance	O
of	O
her	O
musical	O
number	O
“	O
Dark	B-Application
Matter	I-Application
”	O
in	O
her	O
Biophilia	O
concert	O
.	O
</s>
